I use a pair of 10mm box wrenches (11mm works, too) for the same purpose described in the OP as pseudo-dropouts, clamped by the QR skewer. They slide over a front or rear axle and are thicker than the axle stub is long. Very easy to feel the effect of final hub adjustment off the bike.

I’m also a fan of using a pair of cone wrenches on opposing hub cones to ever-so-slightly loosen if too tight, or a pair of 17mm wrenches or whatever fits the locknuts to ever-so-slightly tighten opposing locknuts.