Well my problem with the white was that I couldn't seem to get the right consistency and the product would be over wet and would run as soon as I put it onto the nail and/or one of the sidewalls would be too thick with white product. This was because I kept following the same procedure as I had been shown and didn't wipe my brush after dipping the brush in monomer. It was therefore always too wet. Now I wipe the brush at least once before putting it into the white to remove some of the monomer and when I set it onto the nail, I wait for it to change in texture (a couple of seconds) then pat it to one side, before then patting it to the other side.
Two other tips that I have gotten off here is NOT to wipe my brush on paper after placing the white on the nail or the white will dry too quickly whilst you are trying to manipulate it and the other trick is, once you have patted the white over to one edge, the excess must be patted over with the rest of the white to the other edge. That way, you won't have one side bulkier than the other. These may be obvious to most people, but weren't to me.
Also, you can get a free DVD from NSI called 'beyond the basics' which is very handy and goes through Acrylic, Gel & Nail art. Just ring them up and ask for one.
I hope this is of some help.
Claire x