Likely talcum powder. BUt that's for storage only. In use you need something greasy to let the rubber slide around on itself to avoid ripping and tearing and thus bursting.

Just remembered another option that some folks use. Rubber grease. You may be able to get it from some auto outlets.

WD40 is not a good idea if you want the rubber to last for longer than a day. WD40 has petrochemical solvents in it that will attack the latex based rubber..... although come to think of it there's a chance that the new tan stuff is synthetic and may not suffer like the old stuff would have. Still, if you want to talk about harmful to the operator and flicking around in the model then WD is a good thing to avoid.

If you have the time then using the lube and then laying it out for a few minutes to dry a bit helps limit the fling. Also blotting off any gross excess with a paper towel helps with whatever lube you use.