There's no short answer. Nitromors varnish stripper WILL get the worst of it off and from then on it's scrape away. Try a Sarsten scraper or equivalent (but mind not to gouge the deck with the sharp ends of the blades). After that a sander, but you'll need a fair amount of paper as varnish will cause clogging. Once you're at the bare wood, you then need to decide if you're going to re-varnish or paint. If re-varnishing follow any of the methods given on-line, but you MUST get all the old varnish off if you want a good finish. Make sure the wood is bone dry before you start. Damp wood will lead to the problem you started with.
The first coat should be diluted (if you use Epifanes, then the tin says to dilute about 50%) and subsequent coats accordingly. Be sure to sand lightly between coats to provide a key and TAKE YOUR TIME.
If painting, the base coat (primer) should be sanded down to as fine a surface as you can get - this will help with undercoat and topcoat (but sand down between them, too). Hoover off all dust and use a sticky cloth (home made or proprietary) to remove all particles. Use marine paints as these will give a better finish than standard outdoor paints, although I've had a reasonable finish with these. Try to protect from dust and insects at this time of the year as they will show up on a fine finish!
If your boat is stored in the weather, be prepared to repaint more often than if it's under cover!
Tumshieheid
May 2009
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