First one has to understand the principals behind a silencer's operation
In a firearm, its the hot, fast moving gases that cause the big bang.
To silence a firearm, you need to cool the gases and slow them down.
http://www.canadiantactical.ca/Images/ReflexCutOpen2.JPG
now if you look at the image, the first deflector directs the gas back into the expansion chamber around then barrel.
the rest of the baffles are designed to catch and slowdown more gas before it exits the barrel.
Now for a paintball silencer, its a bit different, the gases are cold and traveling at much lower velocity and there is barrel porting
so you could use a tube and some caps to cover the porting on the barrel (with expansion space inbetween)
but i would buy a Rap4 recon barrel with a threaded tip from Rap4uk.com along with one of their threaded muzzle brakes and attach a homemade silencer to that, so you have a threaded one. (they do offer a threaded silencer but i doubt its effective because it would be illegal in the US if it suppressed by even 1db!