Looking interesting. I also use water based paint for weathered basswood surfaces and will give you a suggestion to age some age to those boards. I sand them with the grain with those foam center finger nail sanding sticks you can find in any Walmart beauty section. I use a very aggressive grit and am always pleased with the end result. You might try a spare board to start with and vary the pressure you apply to have more color left at the top of the boards than at the bottom similar to real life painted stuff exposed to decades of wind,rain and sun damage. Good luck and be sure to post your progress here.