I have a outdoor shed with 2x6 fascia that I think are weather resistant. But they're about 40 years old, and have some splits in them. I'd like to just spackle over those defects, but these boards are unfinished and weathered. and spackle is bright white! Can I get "natural weathered wood" tinted spackle, or can I tint the stuff myself? I guess I could use wood filler, but that's more pricey.