So I know the off-the-cuff answer is you cannot (or should not) use Indoor Rated Poly to weather proof wood as the sun's UV will discolor the wood and other issues visually. This wood though is being used to stack firewood and the way it looks doesn't matter at all. I have about 3/4 gallon of left over Poly and 3/4 Gallon wood stain. Both are indoor use. I'd rather just use those then go buy something new.
My question is can I just go ahead and stain/poly the wood and stack my firewood on top? Will it help? I'm using Douglass Fir wood.
I also have leftover exterior paint but I'd rather not paint the boards. Just a thought.