You should really invest in an air pump, such as a bike pump or aquarium pump. After a few attempts over a few days, you'll see and feel a difference. Some tips from me to you, don't put the aquarium tube too far up your bum. It can hurt, yield worse results, and even scratch your intestinal wall. Just a few inches should be all you need. Also, when you feel the urge to let the air out, just hold out for a second and you'll feel the air go up and the pressure will go down. Really great feeling!
I gave myself a very thorough enema last night (7 full flushes until clear) and then today I was able to do my biggest air inflation yet. I went from 36 inches, to over 40.5 inches (across my navel). I got a little too excited by it, standing on front of my mirror, and I over-inflated a little which made me a little crampy. I had been holding it in so long, that it really took me some time to relax and let most of it out. Now I'm "gassy"... slowly the last of the air is working it's way out. Unfortunately, I know that by the time I fully recover, I'll just want to pump myself full again. After all, tomorrow is Saturday. Ha ha.