sdilts. at the end of the sealing , just put on a last coat evenly with a piece of tea shirt.
Fred's idea is a good one and works. Trucoat and similar products buff out easily but though they shed water nicely, they don't offer much protection from humidity. But the Permalyn provides that.
However, Permalyn is a composite product with properties of a spar varnish and a polyurethane. It both air dries and cross links.
(Which is why you don't use old cans with a skin even if you can thin it. It's not the same stuff.) If you catch it early after a day or two, it's easy to buff. If you wait, it gets hard as a rock, and it hard to work with like a spar varnish.