Big can of worms there. Everything from long soaking sessions in WD-40 to Kroll to Easy-Off oven cleaner to all of the former with a wire brush... to bead/soda blasting. Problem is. you've got a carbon/lead mixture that is frequently harder than the aluminum baffle.
Ultrasonic cleaners can actually pit the aluminum baffle if left too long... so there's that.
Propane torch... lead has a lower melting point than aluminum, but as it's a lead/carbon mix, you can't count on that melting point being consistent with pure lead.
Peracetic acid - white vinegar and hydrogen peroxide mixed 1:1, will remove lead quickly... it will also attack aluminum that is not hard anodized. Cracks or pits in the aluminum? Kiss it goodbye.
What I see with people who have tried all the chemicals and scrub brushes, is that they eventually invest in a small blast cabinet.
175-200 rds ain't much... you can (probably) go 5 times that before the suppressor starts to lose it effectiveness. Flip side is, yeah, it will take longer to clean.
Do your research, or send it back to the mfg. for cleaning. AWC used to do it for free, I don't know about Gemtech.
Cheers,
C