'Get a Rope!'
Errr, while I personally am a 'Do not modify', 'Destroy' or 'Desecrate' my beautiful Lego bricks and pieces type person, they ARE (presumably) YOUR bricks and you can do whatever you wish with them.
My biggest concerns would be that I don't know how well the pieces will fit if the paint is too thick, or how good the coverage will be is it's too thin.... Also there will be potential for the paint to chip and flake, overall I feel painted pieces should be used sparingly and for 'special' 'One Off' or very limited useage.
Your mileage may vary.
Build? I merely Acquire atm.