Inner cleaning?
Piston tops had some hard carbon in need of wire wheel on drilling machine, conical.
Tried to use brass and steel brushes manually as much as possible.
Motorex Drive chain cleaner is a good help. Before, while doing it and afterwards.
Carbonised head, manual brushes and drive chain cleaner. When used drilling machine I avoided valves, since they had no hard stuff.
Brushes for Dremel worn out very quick and fell into pieces not good to get in engine or holes in head.
One head needed to get ex valves removed and brush ports free from carbonised oil.
I avoided the valve seats sealing surfaces.
Very important to protect all holes, oil holes for oil to head most important. No blocked oil flow.
Harder work on chambers might need protection on head surface.
An old head gasket attached on head work fine as protection.
I reshaped a CB750 head's chambers with sanding wheels once using an 836 head gasket as a guide and protection for gasket surface.
Head milled after that.
An old stock gasket if chambers are smaller.
Old used head gaskets good to save for future work.