I've found it takes several months for Rustoleum to FULLY cure, which to me means it passes the can't dent with a fingernail test. That's in the AZ desert, so add more time in humid areas. For a steering wheel I'd recommend setting it aside for 2-3 months.

Matthew 6:33

1952 Chevy 1/2-ton 3100
Late '55 235/SM420/torque tube 3.55
Dalton Highway survivor (using original 216)
www.truckwithaheart.com