The 421 Polishing Compound is a solid compound. A small amount will go a long way! You may also like to try the 512 fine abrasive buff for cleaning club heads.
Though curing that slice is still up to you, you´ll strike the ball much more effectively with clean club head surfaces.
Brass brushes are softer than steel, so you´ll be able to clean away dirt and oxidation without harming your club heads.
Use brass brushes at low speed. The 535 brush is especially effective for cleaning grooved areas. Recommended speed: 15.000 rpm.
Restore a like-new shine by following up with the 423 cloth polishing wheel and 421 polishing compound. Recommended speed: 15.000 rpm.