Yes- Sata or Binks. The Binks Mach 1 was an industrial standard for quite a while, so you can find them used in decent numbers. The Sata Jet RP is a good gun also, and it uses gravity feed, not a pressure pot. The spray pattern is fairly efficient without much overspray or bounce back, but it's not as efficient for materials handling.

Are you going to spray actual varnish, or by varnish do you mean some sort of clear coat? I've never heard of anyone spraying actual varnish, but most of my experience spraying is in a commercial shop using 2-part finishes, so traditional varnish is before my time. You can definitely get higher-quality clear coats that are spray-only, but if you don't have any experience it can get very expensive, is pretty dangerous from a health standpoint, and may not get you good results. Spraying isn't magic- it won't produce a super finish on its own. It's just another way to apply the finish. To get an exceptional finish you'll have to wet sand and buff whether you roll, brush, or spray. If you're going to spray you've got to start somewhere, just remember that in addition to the gun and compressor you need to worry about safety equipment.

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