if you have a vaporiser....smoke the weed then sell it to him...

i wouldn't normally suggest somthing so harsh but it just came off the top of my head and it sounds like a good idea.....i dont know if vaps make any difference to the apperence of it....but if not....

or you could just sell to him fairly and let everything go...thats probly the better way to go....

....or you could just not sell to him! <---best one imo