your the artist you should know how to layer paint! lol. actually i have no idea...2 things come to mind..using an oil based paint and a water based paint might work? or..just try to gently fill it with diffrent colors..might swirl and look neat..even a small cup or something would be worth trying..i dont think you need a whole milk jug. you can shot the container with dang near anything. ive shot milk jugs with 50cal maxi balls and it has the same effect as in the pic. i think that would be awesome with paint..if it worked. or another idea. shoot small cups of diffrent colors. might end up with alot of holes..but thats part of the art! lol. maybe set them up in a line so you can hit them all at once or something...man..almost makes me wanna try some painting! lol