Hello
There is no technique to, through the threads, direct a particular piece.
Yes, there are a number of fillets to be made according to the size of the pipe.
The thread must be conical, so the tap must be for this purpose.
Measure, remove the epoxy paint no further than necessary, make the cone or entrance to the tap and then with the glycerin and lithogirium preparation said joint is sealed.
Being well adjusted, putting the preparation in the male thread (never in the female) you can move it to the necessary point without fear of leaks.
I leave a table of the gas regulation for the realization of the threads.

Regards