I can't say for certain that polish or wax is illegal, but the rules clearly state no foreign substance is allowed on the face. Given that all we are trying to remove is usually simple dirt, water, the universal solvent, is all that is needed. You can use a little soap but a plastic bristle brush with just water usually does the job.

Doing some research, i found this. Consider yourself banned for the next 5 years ;) J/k.. I think you're fine..

www.usga.org/.../equipment-rules.html

Rule 4-2b provides that:

Foreign material must not be applied to the club face for the purpose of influencing the movement of the ball.

The Equipment Standards Committee employs this Rule when materials of a temporary nature have been applied to the face - such as saliva, grass juice, chalk, aerosol spray or similar substances. Permanent attachments or coatings such as plasma spray, "balata"-type rubber or even paint are dealt with under the club face Rules in Appendix II (see Section 5).

The most important question to ask when ruling on a club which has had something temporarily applied to the face by a player is "why has it been put there?" If a material or substance has been applied to the face in order to protect it or to clean it, then it would probably be permitted provided all other Rules are satisfied. However, if the purpose of the application is to influence the movement of the ball or to assist the player in making a stroke, it would be prohibited. Any type of tape or similar material added to the face is not permitted for any purpose.

Keep them clean.Maybe no WD40,unless you get it all off before playing a tourney.

I've been washing my sticks for decades with soap and water with no issues of rust. It's something that I enjoy the night before I'm going to play, sort of like laying out the swords before the batter-ha ha. Knowing that the grooves are clean and the grips sticky gives me a lot of confidence.

I'd imagine you'll be just fine, otherwise there'd be an awful lot of rusty, bare/natural finish wedges on the Tour...

I think it might be illegal. It’s a foreign substance. In my opinion, it’s the same premise of putting a light coating of chapstick on the face. that will eliminate most of the spin. I would think WD40 would do the same. Soap and water, is all you need.

It is standard, common practice to oil some putters and wedges as a preservative. I can’t imagine any performance altering affect on the clubs.
Any residue would be gone with the first divot.