Was hoping somebody out there who has more expertise than me might be able to help me out with my first crack at painting onto fondant.

I need to do a black floral design onto white fondant and was thinking would mix a little black gel colouring with a little alcohol - is this the method that you would suggest - it is for a wedding cake so it needs to be perfect.

Any advice/tricks of the trade would be much appreciated.

Yes, thats how you do it! Make sure you use good brushes, you don't want any little brush hairs falling off and sticking on your cake.

I have painted on fondant several times. I have used pure extracts. Many others use vodka. I want to switch to using vodka, extracts dry too quickly.

If it's for a wedding cake, and you have never painted on fondant before, I would suggest a test run. Days before you have to work on your wedding cake, (less stress!)
Grab a scrap of fondant, grab your food only brushes and see what you come up with. I have to 'play', with the brushes on a paper towel and blot off some of the excess to get the food gel's and the extracts to the correct consistency.

Hope this helps!
tokazodo

I just use straight airbrush color with vodka to think it out if I need to. Works like watercolors.

I use liquid food colours and powders+vodka. I prefer this to gels. Just my MO. I have a painted (purple) wedding cake in my photos plus a Peter Rabbit watercolour-style cake, done using my MO.