No, polyurethane will not work for this. Coatings like vanillacryl will create a hard outer shell that can be sanded and worked. Polyurethane is not a foam coating (and might even melt the foam, I'm not sure) and will not create the outer layer you need. It is mostly used to seal wood and the like. Now, I suppose you could just sand down the foam with very very fine grain paper and paint as is (spray paint will melt it though), however, this will mean that the boomerang will be softer and much more susceptible to damage. The uncoated foam will also retain some texture and can never be sanded perfectly smooth. Putting on a proper hard coat is by far your best option, though you will need to order some online if you cannot find any in local stores (more than likely the case). This website (
http://www.fxsupply.com/materials/foamc ... 7645f56c03 ) sells an alternative to vanillacryl that should work fine, and also sells vanillacryl too, if supplies are available. Yes, you'll need to spend some money for this, but one must always be prepared to part with one's cash if one is to do a proper job. Of course, the ultimate decision on how to proceed with this project is yours; I can only offer advise.