When is the best time to Rub?

[BuyLowSellHigh]

Prexactly HabS!  If you can keep the moisture in contact with the surface then you get the same osmotic effects as in curing or brining.  A well established hotel restaurant group did a bunch of work on developing a signature dry-aged strip steak.  What they got to as their "best" was final trim and cut 3 days before intended use, immediate seasoning, individually wrapped, the stored cold for 3-5 days, unwrap at time of order and onto the grill immediately.  They felt this gave them the best result.

I like ~ 6 hours for things I pre-season with salt containing mixtures.  Doing 3 racks of full spare ribs on the DBS today - they were rubbed at 5:30 and go on at 11:00 am.  If I brine I normally pull it ~ 12 before, get the surface a bit dried and then the rest of the seasoning for as long as I can.

[Habanero Smoker]

I was in a hurry yesterday morning; I forgot to mention ≈6 hours was what Cook's Illustrated found was the point there was no more significant change, so they concluded going beyond that didn't matter. Keeping the moisture in contact with the meat is done by tightly wrapping it in plastic.