Devcon: like Mark says, measure it well, mix the hell out of it for one minute, then mix in a few drops of denatured alcohol. That will give you about 4 minutes to get it on the lure before it starts to get too thick to brush. Once on the lure, it needs to be rotated for the first 45-60 minutes or gravity will cause it to sag. If you don't have some mechanical way to constantly rotate the lure, you can put a hook on the hose and tail of the bait and switch ends every little while it begins to harden. It should take about 5-6 hours to get hard enough to handle at room temperature. If it's still soft the next day, you either didn't measure it accurately or (most likely) you didn't mix it thoroughly enough.
Don't mix more epoxy than you can brush on one or two lures at a time. With experience, I can do up to 3 lures at a time but that's pushing it! You don't want to be in too much of a hurry - that makes for screw-ups. And you WILL want to devise some way to rotate the lures automatically, so start thinking about that.
Two other top coats are fairly easy to use and don't require rotation: UV cured polyester like Solarez and moisture cured urethane like Dick Nite S81. The Solarez requires UV light souce, like a UV bulb or sunlight to harden. The Dick Nite can just be hung up to dry, but it requires a special storage regimen to keep it from hardening in the storage container. Do a search on these options before you plunge in. There's lots of discussions here in Hardbaits on all of them.