Yeah - FINE (5 @ chest) with a subtle side of to side head shake, very slight shoulder shrug (like "whatever" etc) and appropriate facial grammar is what I was going to suggest too
The other one I was thinking of that works, but isn't as clear is a one-handed version of "Doesn't Matter" / "whatever" ("5hands brush back and forth against each other repeatedly ... so in this case just a 5hand doing one "side" of the motion - basically fanning the air with a sideways 5hand lol). It's not nearly as clear - espeically to beginners etc .. however I
might (accidentally lol) use it if I was carrying some books/child etc while chatting with someone I knew reasonably well (so we knew each other's signing "style")