Steve (SR) Johnson shared this process years ago. In (one of his) video's he shows the process if you are are see it to believe it guy. I use it now fairly often myself.
Cork belts can be used with out compound and will give you the finish of the grit - generally. I think they go dull fairly quickly that way and rarely use them with out compound. I also think the finish is a bit uneven when used "plain". That's just an opinion of course.
When you get your first one you will wonder if they shipped you the right thing. It will look very coarse and rough. Cork "gives a bit" and the abrasive is loaded into the cork so in use, the cork gives into the pressure and the abrasive does the work - giving you hopefully a nice even finish. Cork belts are notorious for giving an uneven finish when brand new. You will see errant scratch lines from high spots or large piece of cork. It's hard to screen the cork bits to a consistent size.
The solution is to run them at full speed and push some scrap steel into them with some moderate to hard pressure. You will shave off some loose pieces. This is what you want. You also want to wear down the high spots. If you shave all of the cork granules off, you pushed too hard.
Ten minutes of this gets mentioned often but I've found after just a few minutes the belt surface has evened out. A quick pass or two on a blade blank and examining the finish will tell you if you are done breaking it in or not. Look for uneven lines in the finish. It should be very consistent across the entire pass. Green Chrome compound will come in several different flavors. Some types are drier, some have more wax base and these tend to stick better to the cork belt. If your compound all flings off, try another type. You will get maybe a 50% coverage on the belt with even the stickiest compound. That's more than enough.
I use them because they save time. I can take a 120 grit finish to mirror finish (and any place in between) in quite a bit less time than progressing through several belts. To do this, load them up with green chrome buff compound and give them some pressure when finishing. A light hand here pressure wise will only heat up the blade.
The compound flings all over the place and has to be re-applied in just a few minutes and then you get flinging green stuff all over. Only a portion of the compound ends up sticking. The compound that sticks to the belt combined with the abrasive in the cork sticking out will "smear" the rougher grit finish away.
Buff compounds are generally either cut or color. Rougher compounds cut (black, gray, bobbing), color compounds polish and color (green, pink no scratch and some whites)the steel. Most makers use green chrome on a cork belt as it polishes nicely and gives the steel a pretty blue color. The color is only the way the light reflects off the steel. You aren't really colorizing the steel at all.
The grit of the cork belt matters. Recently I tested a 240, 400 and 800 cork belts side by side using green chrome. You could clearly see the differences in the finish they each left. I now tend to use a 40 or 800 grit belt with cork. If I don't want to get all covered in green chrome (not good to breath in btw - use a respirator) I progress through belts to get the finish I want. Every knife doesn't need to be a mirror or satin finish. It's not a binary choice.
The cork belts tend to last a very long time. The joint tends to fail before you "use them up".
I wear a face shield and respirator of Course.
