Paint sprayer to handle poly?

Any spray gun will spray poly, at least the oil-based type. If you don't have an air compressor, then it makes some sense to get a high-volume low-pressure HVLP system, which will include a gun and the blower unit. Cambell Hausfeld makes one, as do many other manufacturers.

As someone who does a lot of finishing and has an HVLP unit, I can tell you that I don't use it very often. Spraying is often harder than brushing (for instance, inside a cabinet), it is messy, and you have the gun to clean. I really only spray

Instead I finish almost everything using throwaway foam brushes from Jen Manufacturing (the only good ones). If you keep them wrapped in saran wrap in a glass jar in the freezer, they last for months and can be used many times.

Some things I used the sprayer for:

Some things I didn't spray:

a large dining room table a large bookcase with shelves

I have found that you rarely save much time spraying but it is possible to get a superior quality of final coat. This is important on items that won't be given a final rubbing, but not so important on, say, furniture.

Check out the Critter sray unit. About $45. See it at Rockler.com and other woodworker catalogs.