I have. I faced the same problem you described. I have hot air heat in the cellar which creates a lot of (non visable) dust.

In theory Rob (above) is correct. however...Interlux and these paint companies arn't interested in kayak varnishing in your basement. They're interested in selling millions of gallons a year to boaters who varnish their brightwork in the sun in the boating season outside.

If you read the label on japan dryer, it takes very little to speed things up. try not to exceed this. Comercial manufacturers have dryers like japan dryer in their varnishes already, but not the amount you desire. I now varnish in the spring and summer ...so I havn't used it lately. When I did, it worked out fine. The kayak didn't explode. I like to experiment.

Add the dryer to the varnish you are going to use that day, not the whole can otherwise the whole can starts skinning over as I found out.