First this technique will basically give you the feeling of being humped up the ass and humping a nice pussy.
First thing you need to get is a little zip lock bag or condom and lube it up. Then put it over you dick and make sure it will stay on when you start humping! Now get a long dowel (a broom stick will work). On the end of the dowel tape a dildo or the end of a hairbrush or candle, etc. This will act as something to go up your rectum (so make sure it's clean). Take all your stuff to a couch in your house and pull up a chest or coffee table so that it is in front of the couch. The distance should be just enough so that the broomstick or dowel can just barely lie down length-wise in-between the couch and table. Now insert the dildo or hairbrush that is attached to the 'dowel' into your rectum. (Make sure you lube your rectum first.) Know get on your knees in front of the couch and place your dick with the bag or condom over it in-between the couch cushions. Now make sure that when your dick is fully inserted in the cushions that the hairbrush or dildo is in your rectum enough so that it won't fall out. The table is used so that the 'dowel' does not move back when you pull out of the couch. So with the table the 'dowel' is unable to go back when you move back so it's forced to go strait up your ass. Here comes the fun part. Go ahead hump that couch and as you hump the couch your dick is stimulated and as you pull out of the couch your rectum gets filled. It's intense! The chain reaction is when you start humping, the 'dowel' or broomstick starts humping you. Good luck!