100% a must! There's no way you can turn the bait enough by hand to get a really smooth finish.
Don't get me wrong, you can get a finish. but You'll end up with more of the epoxy on one side of the bait.
If your planning on painting baits for a hobby spend the few extra bucks and rig one up. I have a very simple, cheap set up. I'll post some pics tonight for you.