A2 can be sharpened fine on oilstones, it just becomes more important to keep the grind current and work little metal (the same is true for any metal that is very hard - if A2 was 58 hardness, it would sharpen more easily on a lot of the natural stones).

I don't love A2 straight off of a washita (it holds on to a bigger wire edge), but a piece of $5-$10 owyhee or biggs jasper slab is the equalizer in running the burr right off of the steel, and it seems as good as anything else.

That said, someone who uses a guide is never going to get the most out of oilstones and probably won't "get them" because oilstones rely on touch that you're not going to be able to have dragging stones backwards in a guide. Same with someone who feels the need to lap all natural stones. Oilstones don't do their finest work when they've been scuffed up - if they needed that, historical accounts would've involved conditioning them with emery, but I'd imagine the craftsmen involved in fine trades guarded the cleanliness and settled in nature of their fine stones with rigor, and the last thing they would've done is scuffed up a stone.

The best thing anyone who is attached to dragging irons backwards in a guide can do is stick with stones that have tiny particles that don't rely on any touch. You won't have to rely on skill to keep a stone flat, you won't have to have regard for what condition the surface of a stone is in, etc, and you won't have to learn the characteristics of a stone. Just drag the iron across it.

If you want to start sharpening things freehand, though, you will get to the point probably that you can sharpen anything in your house, from scissors, to yard tools, to all of the kitchen knives, drill bits etc, without any guides or contraptions.