I guess the burr type I use the most is a cylinder with a rounded top. The cylinder shaped burr with a flat top doesn't always leave a smooth finish, but the round top cylinder shaped works great.
Cast iron burrs seem to like to run around 10k rpm or so. Most electric grinders spin around 25k at full speed, which will kill a burr right quick, so some sort of speed control is required. A 300W light dimmer switch (very common and cheap) is the easiest way to go.
Coarse cartridge rolls also get a LOT of use in my garage. These remove metal surprisingly fast on iron and aluminum. They also leave a nice finish. They like to be run around the same speed as the burrs. I've got all sorts of mandrels up to around 8" long... so they reach as far as you need.
The first set of heads I ported were done with a standard electric drill and stones... Talk about SLOW going.
Stones are quite a bit slower than cartridge rolls (sanding rolls). I rarely use those anymore.
I've got an expensive full size 1/4"Dumore grinder that has a very small diameter snout, so it reaches places really easy... but it has developed a vibration. Lately, I've been using a couple of those bluegreen $19 Ebay grinders with great success. They are a cheap copy of a Makita. The collets were a bit tight for many of my burrs, but a after a little reaming with a drill, they work just fine. For $19, you just can't beat them.
I get most of my burrs from swap meets. The short ones are usually around $8, and the extra long ones are marked at $15. If you buy a few at a time, it's possible to get a significant discount.
As for the cartridge rolls, I order them by the 100 pak from Travers Tool. They are pretty cheap. The extra long mandrels are made by Standard Abrasives. You can go to their website for the part numbers, then order them through Summit. These are also found at swap meets for $5 or so each for the long ones.
http://www.traverstool.com
https://www.travers.com/catalog/search.asp?ix=445017&sTerms=cartridge+rolls&iSearchType=1&fSearch
http://www.sa-motorsports.com/diyport.htm
http://www.sa-motorsports.com/products.shtm
Good Luck!