I feel your pain, quite literally, as I have both soriatic- and osteo-arthritis. I now find many handgrips very uncomfortable, as they are not shaped for
my hands!
So I've got a bit of nervousness recommending these but anyway...
... a few years ago we had a group buy of Liogier hand-stitched rasps. I have a half-round #11 (I think), also notable because it's cut for a leftie (me!).
Two things stand out about it: (1) the ease and speed of stock removal - it's fast on most things (apart from the very hardest hardwoods, such as Purpleheart), and (2) the quality of finish.
I'd disliked rasps in the past because of the rough finish, occasionally with tramlines. That was in part because they're usually made for right-handed people - it makes a huge difference. Yes, it usually needs a bit of sanding afterwards, but hardly anything (obviously depends on the finish you want, too). It was shockingly good, and remains so, as I look after it very carefully (e.g. cleanup with a brass-bristled brush immediately after use - I don't let oak chips stay stuck on it, nor anything else that might affect the steel).
Ideally a range of grain sizes would be good, but I've been surprised that I don't feel the need for coarser or finer ones than the one I have. I've got a coarser Liogier rat's tail too ("queue du rat"
), but it's too sharp and cuts too fast for nice finishing - a finer one is on the list.
I can see you might get used to a mini-belt sander, but I can also see it would be very easy to wreck a lot of hard work very quickly.
Anyway, you being in France reminded me. I'd expect they'd be cheaper there than here. I must say that such tools are usually out of my price range though - it was only the group offer (directly from M. Liogier) that made them affordable here.
I appreciate that may not help, but if you get a chance to try one, you might be pleasantly surprised.
