I thought I could fix that stuck shutter with just a squirt of cleaner

I was working on a Nikon F3 for a regular customer in my shop last Tuesday. The shutter was sticking at 1/500, so I sprayed some contact cleaner into the mechanism without taking it apart first. That just pushed old grease into the magnet assembly and made it worse. I had to fully strip the top plate and clean each part with pure alcohol, which took over two hours. What's your go-to method for a sticky focal plane shutter when you're trying to avoid a full tear-down?