I'm assuming that you are talking about Z-Poxy Finishing Resin. I've haven't tried thinning it out or spraying. Normally I will mix it and apply it to the wood surface and let it soak into the wood for several minutes. Then I take a heat gun over the area and wipe off all excess resin with a paper towel (some use a roll of toilet paper). Depending on how porous the wood is, I'll sand the piece the next day and apply another coat, doing the same process. Removing all the excess keeps weight down.
Dennis