(I swear this just posted, I saw it, but it disappeared) anyway....

I have 3- 20" squares of 1/4" plywood that have to 100% or darn close to being waterproof! I sprayed them with Thompsons, let them dry, then re=sprayed, ok maybe a really thick coat. but it's been about 5 days, and the darn boards are STILL wet in a few tiny areas, I rub the areas (a few tiny!) but my fingers get oily. They sit out in the daytime leaning against the garage wall in the sun (it's in the 60's here) and at night I bring them in. So, how long is it going to take these pieces of wood to dry? i was then told to spray "indoor use" polyurethane on top for final coat. I'm LOSING it! I had to delay a bed being delivered due to this UGGG (the boards are going to be STRONG support for an opening in the foundation of the platform bed and sitting on concrete blocks. and I'm going to build a deck this summer-god what am I doing wrong?!!? Plz help from anybody!!