There is a bunch of different clearcoats that can be used. I think most use some kind of 2 part slow cure epoxy. The epoxy can be brushed on and then placed on the turning wheel for the clear to dry evenly.
Here is a link with a lot of different info on lure turners and clearcoats.
http://www.tackleunderground.com/community/index.php?app=core&module=search&do=search&fromMainBar=1