I'm installing a new oak bed in a 1952 Chevy pickup. Right or wrong (there are so many opinions out there) I applied 2 coats of Linseed Oil, one coat of stain, then 3 coats of spar urethane. First coat was mixed with 1/3 mineral spirits, then 2 coats of unmixed; now I'm at the last coat. Should I mix the urethane with 1/3 mineral spirits to get a smooth last finish or not? Thanks. Bob