Usually when I create threaded prints, I “print” the thread, then clean it out with a tap afterwards.
I’ve found some of the engineering resins a little difficult to tap, i.e. the tap makes little progress in the print, it gets stuck rather than cutting. What I find that works is to do two things:
(1) Tap the thread before you cure.
(2) Use a little IPA as a “cutting fluid”.
The IPA is especially helpful – previous cured engineering prints that I had difficulty with, tapped-out just fine with a little IPA.