Wet/dry sandpaper is a good recommendation indeed, it should work well with M2. I have some experience grinding M2 and similar grades HSS and it's not as difficult to do well as in the case of D2 or some very abrasion resistant stainless steels. I always strop all my blades, including HSS and stainless. I think it's well worth the extra couple of minutes to ensure a flawless edge.

However, I don't quite agree with the notion that just about any angle will produce a razor edge. Yes, you can put a secondary bevel on a blade at a pretty blunt angle and it will still shave hair. But it's going to be a poor performer at any sort of serious cutting. Straight razors are very thin and hollow ground for a reason. The same reason why the cheap thin blade on the SAK will outcut many far more expensive knives when sharpened properly. A thinner blade just cuts better.

That's why I'm not really a fan of secondary bevels on a knife. After repeated sharpening the actual angle of the edge will get wider and wider as you remove more metal from the bottom and move toward the spine where the blade gets ever thicker. That's particularly problematic with saber grind blades where the primary bevel is often pretty blunt to begin with.