A classic example of trying to extract cheap humour by naming a simple drink in an excitingly lewd manner. Slow - that's for sloe gin. Comfortable is for Southern Comfort. Screw is for screwdriver (vodka and orange juice). The alcohol flavour isn't so much masked as mixed up to confuse you.
By combining this with a Harvey Wallbanger you can get the even more exciting 'slow comfortable screw against the wall'. Tiresome to say, lethal for the liver. Definitely a bloody good drink.