This another idea that has worked real well for me and I was using this today and decided to share.
Most of us know that hollow axles do compress a tiny bit when we clamp the QR skewer, so I really don't "sign off" a bearing adjustment until I've checked under compression. And that's a PIA if you can only reinstall the wheel into a frame to get that compression. So I've made two sets of clamping handles, one wooden and the most recent from aluminum. I like the aluminum set best. When I've had a hub apart, such as during an overhaul, I reassemble the hub leaving the cones a whisker tight, then snug the lock nut. I then use cone wrenches (13 or 15mm) to turn the two cones out against each other a whisker so the adjustment loosens and feels right - just the barest bit of play.
I then install these handles on the wheel and clamp with a QR. I hold the assembly on the edge of the bench and "clock" the wheel: turn it slowly and watch it rotate, slow, change direction and rotate again, sometimes two or three changes, like the heavy spot is a pendulem. No play and even, smooth direction changes tells me its done. Lately I can achieve this on the first try or maybe with one correction. If a correction is needed, I loosen the QR, adjust the cones, close the QR and check again. When done I tighten the lock nut fully and check again just to be sure.
No, its not hanging in mid air. My hand is holding the wheel, stage left.
The dimensions are not critical but the hole should be close to the 10mm axle diameter (I drilled a 3/8" hole as I have no metric drills), the thickness should be greater than 5mm (mine is 6mm) and the dimensions should be a handy size (mine are 7mm x 3.5mm as that's the scrap piece I had). The bottom pix shows them on bench. I've prepared two QR skewers with any plastic removed from the nuts so they spin on quickly. One long one and one std front skewer. And these handles are nice when you want to spin up the wheel to hear/feel how smooth the hub is. Always a good final check.
BTW, my daughter-in-law works in an OR and they use those small white plastic trays for something, throwing out many per day. She salvaged a couple for me. Handy as the bearings go in the small compartment, the small parts in the medium one and the large parts in the large compartment. Handy for keeping things organized, especially when you're doing a pair of wheels and NEED to keep things where they belong.
Oh, yeah, those are two vintage VAR cone wrenches that came out of a barn (literally). Nice and I'm glad to have them.