My bag has a mechanism for attaching the extra strap you pull through to tighten it, to the bag. Its pretty convenient. With all other compression straps and such I use rubber bands, zip ties, or twist ties to keep them under control. When its raining they always find a way to drip down the back of my socks...

I'm not sure what you mean about the t-shirt either. I don't have problems like this.

Also, life is a lot easier when you have things in the bag. When a messenger bag is empty it is a horrible thing to try to get it to fit right... especially if it is a large one.