Sanding is always best, but anything will dull the sheen, which is really what you want. You also want to remove any grease, grime, dirt...anything that may get in the way for the paint to grab hold. You can do that by washing if you don't want to sand...many people will do both. You don't want to use steel wool becuase the small bits of steel that get left behind will rust out with a latex paint, but you can use the synthetic pads that are available now. Still, sanding to me doensn't make that much of a mess, does it? You are only sanding enough to dull the sheen of the existing poly. It really shouldn't make that much dust.

thanks paintguy. Poly's not that thick and it was satin. I'll rough it up quickly with a sanding sponge and then the tack cloth. Thanks for warning me off the steel wool.