OK, everyone. I can't believe that no one has tried this: Use 3 or 4 inch wide masking tape. Lay two or three strips, sticky side up, on the area where you don't want your cats. When they jump up on the tape and it sticks (rather well) to their feet and fur, they will think twice about getting up on that surface again. So, for my kitchen counter, I cut the tape about 18 to 24 inches long and lay them along the entire lenght of the counter, two or three deep, right on the edge (hope this makes sense)so when they jump up they land on the tape.
The best part is when it happens, you are not in the room and they can't figure out what happened; and you don't look like 'the bad guy.'
Three of my cats only needed one lesson, and the fourth one needed a reminder about once a year. Much easier then carrying around a spray bottle.
I found that life in the sewing area is better when I don't tell them "no", but give them a space of their own so they can 'help' right next to the action, rather than in the middle of it.
For the rest, cover your machines and WIP's and use lots of lint rollers. And at the end of the day, hug your assistant.