Painting - Protective finish for outside items

My neighbor has purchased cows, yes - cows, made of resin. They are painted flat and the only thing the manufacturer can tell him is the paint is made in Taiwan, not whether it is water based or oil. I think it would be water based. He has asked me to spray a protective clear coat on them that will help keep the UV from fading the paint too quickly. I need help pointing me to a product that I can use. He tested a small spot and the paint bubbled. I would assume that a urethane product would cause that. ( He disposed of the product so I don't know). Any help would be appreciated.:confused:

A clear coating would not really help to slow UV damage to the paint as the UV would still pass through the finish.An exterior grade spar urethane would act as a longer life protective finish but not stop UV reaching the paint.The bubbling suggests either that the existing finish is not a conventional paint and/or what was tried was somewhat more exotic like lacquer etc and reacted to the existing finish.Poly would not cause either latex or oil paint to bubble.

Your best bet to protect this item is to repaint it with a high quality exterior grade enamel or house paint and since you don't know what's on it to prime it first with an exterior oil primer.

This is a product I always use outside, I've done church doors and teak on my boat, both are on 15 years without any UV damage. It does have an amber tone, so you'll have to decide if you can stand that. And I don't believe it will react with whatever you have on you cows to start with.......

http://www.prattandlambert.com/pdf/product-data-sheets/7901.pdf

There are also waterbased exterior varnishes which boast UV Absorbers, by General Finishes Exterior 450 on Amazon, but I have no experience with them.