I’m not aesthetically prone when it comes to fly tying, but half way through my latest swap tie…finally learned what I have to do for an acceptable
wet fly/streamer collar hackle.
I agree. Tying the same pattern repetitiously (as one would likely do for a swap), allows you to “tweak” your technique.
I often think of a better way to do a certain part of the fly during the first tie. That one gets thrown out. I apply the new technique on the rest of the flies, and that new technique has a good chance of carrying over to other patterns.
Sure beats the “one-off” patterns I sometimes produce. HA!
I agree. The few fly swaps I did, sure helped me tie those flies.
Like the Klinkhammer special for example, I pretty much sucked at it, but with some practice I did an acceptable job.
Good hackle also helped a heck of a lot. 
One of the best things a new tier, or any tier, can do is join a swap. Nothing builds confidence and muscle memory like tying 12 or so exact duplicates of the same fly.
One of the bes tthings for me in swaps is all the different flies that I get back.
Also the new materials that I get to see.
Rick