Only thing to do is try it and see how well it works. Things to look for is how much swarf (black/grey streaks of removed steel) is taken off. Gesswein has a pretty good reputation. I've used similar from another co - same size, color and tube but that means very little. It worked well, material was oil based and reasonably aggressive.
You need to decide what effects you're looking for in a compound. A cheap and easy backing is to simply wrap a sheet or two of copy or writing paper around a regular combination bench stone - rub the compound on that. The oil based diamond will need to dry for a few, regular grease stick, crayon types are good to go. Swap it out if it becomes loaded up or you don't like the effect.
Flexcut Gold is on one of the better manufactured compounds out there. IMHO diamond doesn't work any better than AlumOx based materials on most steels until you get into the high Vanadium carbide varieties - even then, backhoning on diamond lapping film from 3M is (again in my humble opinion) a better way to go compared to stropping. 6" sheets can be had for about $6 a sheet.
