Re: Cheap refinish
Umm, you might be hard pressed to find anything that will stick to the bedliner, on the interior or the exterior of the boat's hull. I hate to say it, but maybe more bedliner? It'll get heavy though, so I probably wouldn't. You might try rattle can Vinyl/Fabric dye or 1 of the new plastic patio furniture spray cans. Depending on the make up of the liner you used. Some are more plasticized (harder) and some tend to be more rubberized (flexible).
But either way, you'll need a specialty paint, and some through prep to get anything to stick to the liner very well or for very long... just IMHO.
BTW: It took me FOREVER w/ very harsh/toxic industrial stripper to remove the bedliner sprayed on the entire interior hull bottom of my Jet..... It was not a pleasant experience.