I don't know. I use photoshop just like everybody else. Convert to bitmap, linescreen.
What I do differently than some people I guess is I use different linescreens for the same color pretty often and I use what I know about process printing and simulated process to overlay dot patterns.
Like...on this Supersuckers poster...the type has a totally different dot pattern than dude. And if you actually see the print and stand back like ten feet you stop seeing the dots...which I think were like 15 or 20 lpi and the skin looks like flesh.