Do you have any advice for plying? I have started spinning again after leaving the wheel for many, many years. I'm thinking that these first few bobbins of yarn aren't going to be as uniform as I would like, so plying might make a better overall yarn.
A: Yes plying will usually help an irregular yarn. As far as plying hints go, my simplest recommendation is to ply until the yarn looks good. Of course if you spun Z (clockwise) then you will ply S (counterclockwise). The two parts will nest together and both parts will puff up a bit. If the yarns are under-plied then the two parts, look thready not really nested. If the yarns are over-plied then they both begin to be compressed and get tighter, there will be less definition between the parts. Counting the treadles can help in the consistency but watching closely is best. If you have a double drive wheel then the yarn continues to ply as it is pulled into the orifice. If it is a single drive then you can usually pass the yarn in quickly without adding much plying twist.
It is also helpful to not pass the yarn all the way into the orifice. Stop when the newly plied yarn still extends about 8 inches from the orifice. With your forward hand pinch that spot while you tension the next length so that both parts are equally taut. Then let the plying twist advance up the new length counting and watching the twist. When it looks sufficient let it wind unto the bobbin.