Hi ladies! Unfortunately, my sewing machine is down and out for the count. Hopefully I'll be able to fix it, but otherwise I will be waiting on a new one to arrive. So, although I couldn't take the pictures and describe it myself, here are some links to some nice tutorials on both a wetbag and a pail liner.
Wetbag with cotton outer: http://littlebirdiesecrets.blogspot.com/2009/05/wet-bag-tutorial.html
For this wetbag, she uses vinyl, but you can also replace that with PUL. Just make sure that when you are sewing that the laminated side of the PUL is facing inwards to where the diapers would touch.
If you want to make it a hanging wetbag, you can buy a nylon strap from your craft or fabric store and attach it at the top, using snaps or velcro so that the strap can make a loop.
And even easier, a pail liner: http://themombot.com/crafting/2011/08/15/diy-diaper-pail-liner
These aren't exactly the way that I was going to write up a tutorial, (and in fact I prefer using french seams for my pail liners because I think that they are less likely to leak, so if you know how to do that, I highly suggest it) but they look like they would work very well.