My father used to build sports cars and taught me this neat trick how to get carbon, dirt, etc out of an engine cylinder (with the pistons in the engine).
Turn the crankshaft until the 1st piston is at the bottom of its stroke,
Then wipe the cylinder wall down with a heavy oil (straight 30 wt or heavier) then turn the crank until the piston up until its about an inch from the top of the cylinder and stop and turn the crank in the other direction.
As the piston travels back down the dirt etc, will remain suspended in the ring of oil running down the cylinder wall and you just wipe it out with a clean rag.
Then continue until all cylinders are clean.
This method traps the smallest particles.
Using a vacuum 1st would be a good idea.