My edge angles have already been set and I'm just trying to sharpen them up before my next ski trip.
You always need a guide except for hand stoning any raised burrs that rocks have knocked out in your edges, and a stone with a guide is better. The rock pushes the metal out and work hardens
it, not case hardens. In any case, that part of your edge steel is harder than a file and needs to be removed either by an abrasive stone or a diamond file.
What is your goal? Just clean, sharp edges for daily skiing? All you need is a guide for the correct angles, a hard file made for ski edges plus a file handle, a coarse or medium diamond file, and a fine abrasive stone. For the bottom, you just want to remove burrs, you don't want to remove metal. That's the job of the yearly shop tune. On the sides, you need to remove burrs first, then remove lots of metal with the file if absolutely needed, then smooth with the diamonds, then polish with the stone. It should only take a few swipes with each. It is best to stroke from tip to tail. The file must only contact the edge in the cutting direction. With the file tang & handle in your right hand, push. With the file tang & handle in your left hand, pull (draw filing). Don't let the file drag on the return stroke--it dulls the file teeth. A few low nicked spots are OK for rec sking (we aren't racing on ice, are we?) as long as there are no raised nicks. If the edge is sharp enough to drag material from your thumbnail, quit.
A good routine is to coat the edges with a black felt tip marker. As you sharpen you can easily see what is cut away and what isn't. The tip about water or secret sauce is to coat the diamond file and abrasive stone so it doesn't get loaded (pores filled) with the steel and fiberglass from the ski edges.
What are the correct angles? I like 1° on the bottom edges and 3° on the side edges. Others like 1° & 2°. Whatever, find out what the shop did and keep those angles unless you have a reason to change them. Buy guides for the angles you like.