JC, You're ahead of the game with new. sharp taps. As soon as the tap starts to bind STOP, back it off a bit, clean off the cuttings and more cutting oil. Have gotten through some pretty hard steel with carbon taps but all the back and forth can try your patience. pretty easy to get frustrated and snap a #6 tap (though I've come close with a ¼").
Bought a can of Brownell's Do Drill years ago and it's almost gone. The stuff just works and has the proper sulfur and oil machine shop smell. Don't know but I suspect any name brand is fine for your job. Had a gunsmith uncle who was fond of STP.
