Doubling / tripling will depend on the project. Usually I choose very light Merino for bracelets and the like (it's not a good choice for slings and it might be tricky to work with for beginners!). I don't remember the weight.
Regarding slings, I've made good experiences with sock wool. 170 g per 100 m, 3 ply. 24 strand braids usually, single string per strand (i.e. not doubled).
JudoP wrote on Jan 12
th, 2021 at 11:40am:
I'm working with the card at the moment and not sure if multiple strands will work very well with it(?)
Do yourself a favour and throw the card away, and go fist-supported braiding or marudai
You will curse a bit more in the beginning, but it is worth it in the long run. I never got along with the card. It's slow and proper tightening is a pain with the card in my opinion.
JudoP wrote on Jan 12
th, 2021 at 11:40am:
I've done some small fist braided 8 strand stuff with thicker nylon cord and seems ok, but I can't get particularly good tightness even pulling pretty hard after every pass.
Pull/tighten mainly the lowers. The uppers don't need to be tightened, but just be firm-ish.
Thin-ish slippery cord can be tricky to tighten.