The 28 and 29 windshield frames had a small tube, maybe 1 1/4" long or so that the hand wiper went through. I don't think there was any bushings or anything else that were used. I could be wrong of course. Windshield on Model A's with hand wipers used the small tube, model A's with vacuum and electric wipers just had a series of holes in the top of the windshield frame.
My mistake, I misread your post as a CCPU wiper question. Never mind.
Rusty Nelson