Similar situation recently. I found a dime-sized indentation in the dust cap of an M2. I didn't trust myself using the vacuum, so I used strong duct tape (gorilla) cut into narrow strips. I was worried about it sticking too well, or leaving residue, but neither happened. Took about 10 minutes since I was being extra careful, but came out good.

Marantz SR7010
DIY HTPC
M60 x2
RP-450C
QS8 x2
QS10 x2
M2 x4
EP600
Samsung QN90A 85"