A grinder doesn't have the power that you really need for buffing BUT it will work. You just have to lean into it and then let it catch back up and lean into it again. Particularly with the looser wheels. (loose cotton or spiral cotton) It will do ok with the sisal. (the rough sewn pad)
As for polising, I wouldn't use the buffer on chrome unless you're using a compound that doesn't cut at all, only color. The 5 might be this type of compound. You would use a loose cotton wheel with this.
I don't know about your numbers, but a black bar/compound is corse, brown is medium, and white is fine, and red (rouge) is extra fine. Always use a different pad/wheel with each compound. Never use the same wheel for two different compounds. Always clean the parts between compounds too. (wipe them down)
For levers (and most aluminum), I'd use a black (emery) compound to get them smooth then use a brown (tripoli) for the coloring and then a white (rouge) for high polish.
Number one rule, cut away from you (hold the part on the bottom of the wheel if it turns toward you or on the top if it turns away from you so that if the part flys it flys away, not toward you.
Number two rule, HOLD ONTO THE PART!! When you're bearing down on the buffer, the buffer can grab the part and rip it from your hand. I've done a lot of buffing on my stuff and I've had a riser thrown twice causing me to have to do a LOT of work to repair the damage by sanding it out.
Use basic safety rules too for rotary tools:
Never wear loose clothing
Never have dangling drawstrings, jewelry, etc.
Wear gloves (parts get hot)
Wear safety glasses or shield (you're cutting metal off and it's flying around)
I wear a paper breathing mask because of the airborn grit.
This stuff is messy, put the buffer somewhere that you don't care if grit gets all over stuff.
That should be a good start..
