bes way to do it from my knowledge go to invite only session your the host because you higher level get a helicopter and if you look on your map at the very top you should see a small island the reason you go here is to make sure he spawns close then call lester put the highest bounty on your friend and wait till message pops up on screen then kill him keep putting bounty and kill him,if this does not work another thing you can do is go to missions host mission go to potshot and put it on the hardest level once you have finished mission and it gives you your xp keep rapidly tapping x on xbox and i think square in ps3 then just start mission over again,hope this helped if not reply your gamertag and i will help you tomorrow

the thing is i cant even put a bounty on my friend it doesnt show his name