Thanks for mentioning the Tulip Fabric Paint - Midnight.
Here's a link to the thread that contains some discussion with a link to a good article:
Tulip Fabric Paint Eyes
BTW, once made, a fabric paint eye can be affixed to most any suitable jig just by 'sticking' it on and then applying a clear topcoat to the entire jig head. What I like most about them is that a jig head doesn't have to be recessed. This eye will form and stick onto most any jig.
One of their limitations, to me, is that I find very small eyes to be difficult to make with round, well-formed pupils. My very best results are suited for 1/8-ounce jig heads and larger.