I used brake cleaner on my prommy before the beginning of this season. BB scum buildup was quite bad. Don't do it with any rubber, plastic or silicone exposed of course. It's supposed to be silicone safe but... meh. I redid my rhop patch at the same time.
At some point I will solder up a copper pipe so I can submerge a whole barrel to soak in acetone or similar cleaner.
Swabbed it out after the brake cleaner and all was shiny once again. The swab came out nasty though.
I futz with V2s, V3s and V6s. I could be wrong... but probably, most likely not, as far as I know.