I'm not sure if it will help but when I painted my canopy I sprayed it with a outdoor primer to help seal the wood and give added protection. I then painted mine black. I used 1x1's and built a frame that sits inside of my canopy to rest on the top of the tank and then I mounted the wood to that. I bought 2 sheets of the cabinet grade wood from home depot and they were like $25 per sheet or something like that. They turned out really nice and gave my canopy a pretty clean looking finish IMO.
here are some pics of it:
http://www.aquaaddict.org/Tank/Tank2006/DIY/canopy/