As with all my neon colors they work better with a sponge, otherwise you really have to layer them with a brush. The neon rainbow one stroke also doesn't allow you to pick up all the colors with most flat #12 and 3/4 brushes. So I end up having to choose which side and color I want.
I wouldn't buy it again, in fact I took it out of my kit because the kids see it and always want it over a regular rainbow or Leanne Rainbow (which are WAY better). Just like I did the kids lay eyes on the Neon Rainbow one stroke and think it's going to look amazing, and then get a bit disappointed when it doesn't.
Picture here: Lies
Oddly enough the 'cocktail' neon split cake I don't seem to have too much of a problem with!
The neon rainbow one stroke still has it's uses though; with a sponge it's great for applying neon rainbow eye shadow, or a small neon rainbow area in the design, even as a rainbow if you use a sponge. But the lines are never as crisp as with a brush, no i usually use a different rainbow one stroke for ease and convenience.
I couldn't live without my homemade Leanne's TAG rainbow one stroke cake! What a time saver! Such a rainbow cheat, I love it to bits!
Only two of the colors are neon so it seems to work better.
Don't turn your back on buying neon colors altogether though, like I said, when you have the right tool (like a sponge) you can make some pretty awesome stuff.