DON, KRAIG - I have a Dewalt 4-1/2" grinder that I bet is over twenty-five yrs old. I've replaced the cord twice and it needs another new one now. That's all I've done to it, it just ALWAYS works. It's my grinder of first choice. I also got Dad's old Dewalt 4-1/2", same model, only older and more beat-up and it's my second choice. I bought a Milwaukee Magnum 15 amp 4-1/2" angle grinder several years ago. Ohhh does it make the sparks fly! It's longer than the Dewalts by 4-5 inches which makes getting into tight places a problems sometimes. Then I have a 7"/9" 6000 rpm Black & Decker angle grinder, 15 amp, 4 HP motor. BIG heavy sucker, weighs 20 pounds with a 7" disc. I don't use it much! Then I have a 1/4" Craftsman die grinder, (Think Dremel on Steroids!), 3-4 Dremels, and three 1/4" air die grinders.
DON - I use those flap wheels A LOT! They work great on steel or wood. They're great for preparing edges for welding, and also dressing ugly welds you don't want anyone to see.
DAD used to buy his abrasives in BULK from Harbor Freight I think. He snuck a couple big boxes of thin cut-off wheels, grinding wheels, all kinds of stuff into my truck four yrs ago. I haven't begun to use up a quarter of them yet.
The knotted wire cup brushes work great for paint removal. But I'd wear a surgical mask safely glasses AND a face shield when using them.
They also sell a Scotch-brite disc or wheel that's good for paint & rust removal. They don't scarf up the base metal, just remove the paint & rust and shine up the metal. I've also used what's called a "Zippidy-Do" wheel, attaches to a mandrel that chucks into a drill, it's a semi-rigid abrasive coated mesh wheel that really cuts paint & rust but will scratch the base metal. But they will not load-up with old paint. The abrasive wears away fast enough you always have clean abrasive cutting.