Life is much more fun when you have teeny moustache's on your nails! To do mine I used Rimmel 5 in 1 base & topcoat and Revlon 'white on white' (050) . Then I cut off the tips of a cocktail stick and filed them with a nail file to create a dotting tool. I dotted Sally Hansen's 'gray by grey' (350) and 'plums the word' (360) on 3/5 fingers. To do the teeny tache's I dipped an old eyeliner brush into a drop of Revlons 'Black Lingerie' (919) and painted two flicks in a sort of 'w' shape, then filled in the top of the moustache with another two flicks. Then finally I finished with a topcoat.
Painting freehand onto your nails takes practice but I think that if you have a clear idea of what you're doing then you should be ok. A step by step plan of the strokes you'll use to create your design is really useful, try painting onto paper first.
By only painting on 4/10 nails I cut my time way down, even though the moustaches aren't particularly hard and I do love spending time painting my nails, I think if I'd done one on each nail I would've been there for a long time. Alternating and doing cute dots on the other fingers saved me a lot of time (and stress probably).
When painting freehand like this I find that it takes a long time for the polish to dry, so make sure that you let your pattern dry completely before painting over a topcoat. And when you do paint on a topcoat be careful not to pull at the polish, even though it might be tough dry it may still pull with your brush.