The Flying Double Sheet Bend is the knot to use when you want to extend the tow line for your dinghy, or tie on another length of line to your anchor rode. It is much less likely to loosen itself up as the line gets worked back and forth.
I use the Round Turn and Two Half Hitches more frequently than any other knot. It's perfect for fenders, and perfect for tying up the dinghy. Any time there is a load on the line, the round turn takes the load and you can finish it easily with the half hitches. I use a variation that I haven't yet seen elsewhere, by making the second half hitch in the opposite direction of the first one. The result is a knot that is more compact and stable - meaning less likely to loosen itself up as the line gets worked, and that makes it more secure.
The Sheet Bend joins two lines together, and is particularly effective with lines of different diameter. This knot is actually a bowline, and is tied using the same method as the Flying Bowline. When the jib sheet parts on the way to the weathermark, this knot will help you tie it back together in a hurry.
This method for tying a bowline is the quickest and easiest method there is. Once you learn to tie the Flying Bowline, I think you'll forget any other method. You can tie the Flying Bowline at the end your reach, overhead, even blindfolded, and sometimes, that really counts.