I finally figured out how to save a partially used can of Permalyn finish or sealer. The last gun I finished was two years ago. The gun I finished last night was sealed and finished with old cans of the stuff. Two years ago, I went into my garden, collected a quantity of pebbles, clean and dried them. Then placed them into the half filled cans in order to raise the level to the rim. Covered the rim of the can with plastic wrap, placed pipe tape around the threads and screwed on the lid. Actually, I was kind of surprised that it actually worked and expected the finish to be hard as a rock... as it usually was.
Don't know if this has been covered before... If not, hope this helps.
Decker