Get the look: Pat McGrath makes up a model before the show

How does make-up artist Pat McGrath ready an army of models for a fashion show? Harriet Walker goes backstage to find out

The look that make-up artist Pat McGrath is creating backstage before the Dolce & Gabbana spring 2013 show and the atmosphere she is trying to create it in are singularly ill-suited, I can't help thinking.

The former is all languor – sun-kissed beauty, untroubled by work or worry, fresh from a Sicilian beach or market square. The latter is frenetic, fast and noisy: models and dressers rush here and there, between banks of mirrors and clothing rails, a breakfast bar and a chill-out area. The rrrr of hairdryers is constant and, if not deafening, then low-level irritating to say the least.

"It's all about Sicilian summertime," explains an unruffled McGrath, one of the world's biggest names in backstage cosmetics and the talent behind thousands of iconic and iconoclastic catwalk make-up looks. "Lovely gold colours everywhere. You can see in the clothing…" Here she gesticulates to a whole other section of the room, where an entirely separate army of people are steaming and preparing the garments that will stride down the runway that afternoon.

"Beautiful, bold patterns on the clothes, all really pretty. They [the designers Domenico Dolce and Stefano Gabbana] just wanted the girls to look sun-kissed and beautiful."

And they do. The models milling around are half-ready, most of them made up already with brightly coloured Sicilian silk scarves wound into simple and classic chignons, wearing black satin Dolce dressing gowns before they climb into the luxurious clothes waiting with their names on them.

To achieve the golden glow on each model's skin, McGrath's team has mixed three shades of blusher together – Soleil, Mocha and Apricot – swept across the cheeks and browbone, and highlighted the eyelids with a pale shade taken from the brand's best-selling Desert Quad compact.

"We sit down with the designers and they show us the collections," says McGrath. "They show us the fabrics, talk about their inspirations, talk about Sicily. We know it quite well because we were all there for the couture show in July, so we remember those fabulous colours, and how gorgeous it all was."

Dolce & Gabbana are regularly inspired by the glamour and opulence of their native Sicily; each of their shows is a paean to the homely – not to mention high-end – sophistication of that area. But their spring show is entitled "Fatto a Mano" or "handmade", with models wearing hessian-style bustier dresses featuring flour sack motifs, and rustic-looking wicker hoop skirts inspired by the artisan crafts of the region. Consequently, there is an undone elegance to the make-up: not too heavy or exaggerated, despite the fact that models will be walking under huge banks of lights and snapped by hundreds of lenses at the end of the catwalk.

"I'm lucky that we have such fabulous tools," McGrath says, gesturing at an array of make-up brushes laid out like a surgeon's kit on a table nearby. "They don't allow the product to go on in splodges because they have these perfect ~bristles. And they're made not just for make-up artists but for real women, to make it easier. You should always use a foundation brush to put your base on, and these are really good ones."

"The products are also very transparent and easy-to-use," she continues, "which means they're more mistake-proof. With foundation, it's always good to buy two, as you go from spring and summer into winter, and mix them together throughout the year."

McGrath's advice is to pick a summer shade that is slightly brighter than your natural skin tone, and a winter one that is slightly warmer – that way, you don't have the aggravating shift between glowy and ghoulish when the weather takes a turn for the chillier.

"Because then you don't start thinking 'oh my God, I look awful' and wandering round the department store looking for another brand!" she laughs. "No, darling!"

Broadly speaking, make-up trends don't change all that much between the obvious warming up for winter and easing off for summer, but show make-up tends to be more flamboyant than what we mortals might slap on to go to the shops in. McGrath's strength is in being able to flit between the two, to create wild and wonderful looks at one show (the scarlet masks she painted at Viktor and Rolf's autumn 2011 collection spring to mind) and something much more wearable at another. Earlier in the week she created a matte and minimal look for Jil Sander's show.

"I'm seeing a lot of bold minimalism," she agrees. "The fact that the skin was minimal and then there's something else going on, maybe a bold mouth. Then there's a nude trend, where everything's just tone on tone, and now we're going into this flushed, healthy look too. Keeping things sexy and fresh is very much a couture look – the stained lip, instead having a very hard line, for example. Doing things softly makes it all look more modern."

McGrath's other fail-safe tip is to sketch out eyeliner with a pencil before you start with a liquid. The Dolce & Gabbana models' eyes are accentuated with the perfect, subtle flick of black – perfected in removable kohl first and then traced over in ink afterwards, with McGrath using a tapered cotton bud to perfect the angle of the flick.

"First of all, just dot with a pencil and then draw the line, with your eyelids down – open your eyes and have a look, see where you like the flick to be and then use your cotton bud. In the swoop and the adjusting, you get it in the right place. Every girl wears eyeliner these days and they do it so well, don't they?"

I realise as she says this to me that my own eyeliner is horribly uneven, and I don't have anywhere near as stressful an excuse as the environment she has been working in for the past two hours.

But Pat McGrath is feeling charitable. "You've done good with yours today!" she smiles. "It's sexy like that, a bit of wonky eyeliner! Yeah!"

And with that, she turns to perfect the 158 flicks on the 158 eyes of the 79 models in the show.