Traditionnally it is squeegeed across a carefully cleaned/degreased mesh screen that is laid over custom sized platten to suit the screen frame, or the screen is inverted, and the coating is done from the reverse so that the emulsion pressed thoughthe screen can be recycled back to the storage bottle.
Mask with a high contrast negative, rubylith, or whatever else, and apply a liberal amount of UV for a relatively short time, or more pedestrain amounts for a longer time (sometimes days).
Yes, wash gently with water.
I think some shops would uv expose agian to toughen any edges up.
It can be removed after to reuse the screen, but a lot of shops would just re-mesh the reusable frame.
Frames can be trade specific round aluminum bars that crank to tighten the screen, or wood frames which the screen would be stretched over, and then stapled or clamped into the frame.
I have an automated pneumatic powered screen screen stretcher pressure regulator and auto recycler controller (of mid 70's era I estimate) and four 6" wide clamps and all hoses bought for $20 a few months ago at an auction, open for sale to anyome for the $20 and shippng costs.
Then use the washed and hardened screen as a mask to squeegee ink/paint through.