Starting with a flat bar of your favorite steel, you have to remove everything that doesn't look like a razor.

That can be accomplished with what ever method, belt, disk, files, chisels, stone wheels you choose. This part of the process does not make any difference. Really, just use the tools you have and get good with them until you can afford better tools that do the job more effectively. You can abrade away material to your heart's content at whatever speed you wish. Grinders will heat up the steel and turn it all sorts of colors, but by that time it will be too hot to hold anyway.

Once the blade has been heat treated, then grinding can dictate a different approach. You don't want to get the blade hot enough to temper away the hardness of the blade.

Wet grinding addresses the problem of heat generated during abrasion and helps to protect the investment put into the heat treatment. You can use a belt grinder running at a slower speed, aka variable speed. But, have a bucket of water handy and work with your bare hands so you can feel the moment that the steel is warming up and cool it right away.

Files are good steel for the most part, IF they are old ones like Nicholson or Black Diamond. Some of the new files are case hardened mild steel and should be approached cautiously. Grinding a blade from a hardened old file will be more work since you have to grind away hard steel and you have to attend to the heat problem if you don't want to lose that hardness. It will take longer in terms of time invested.