I use this
http://www.credo.fr/uk/accessoire_cr...ar_glue_uk.htm
http://www.amazon.com/Credo-Torcedor...mg_top?ie=UTF8
I got it off a CC site so cant relly link it here. It works well, was firly inexpensive and has a nice little "nail polish" brush. Just gently peel the wrapper back and apply sparingly.