another thing i do for these types of situations is use Qtips to clean the threads. spray your cleaner then spin the qtips around and repeat with new qtips until clean.
might be worth a shot?
I have never used a Q-tip to clean threads. Like I said, I use solvent - carb cleaner, brake cleaner, paint thinner, lacquer thinner, acetone, or MEK. I brush the threads with a wire brush, apply some solvent, then blow them off with compressed air, then run the chaser over the threads, clean with solvent again, and blow them off with compressed air. Trust me... those threads were practically sterile!!