Re-wind singles bobbins for extra smooth worsted
If you’ve spun worsted singles and you want an extra smooth plied yarn, re-wind the bobbins of singles so that you are plying in the same direction as you did when you spun.
Think of it like smoothing down your own hair in one direction, then if you don’t re-wind you’ll be floofing the hair up back in the wrong direction when you ply. If you re-wind, you’ll be smoothing the hair down again with your fingers as you ply.
Bonus points if you re-wind over a long distance, as this helps even out the twist in your singles too.