Crochet Best yarn (brand? weight? whatever?) for tedious little doll projects?

I guess the first thing to ask is, how small are you willing to work?
As dolls are so much smaller than people, stuff with even worsted weight yarn can end up looking bulky or like they were done with BIG chunky yarn in comparison to the doll. But since that's a thing real people wear, you can definitely use that kind of yarn- however, for the most In-Scale realism you'll want to go as tiny as you can sometimes. I have seen TINY things crocheted out of tatting thread.

 

I sugest checking out the crochet thread. Yarn is discussed quite often there and a lot of people mention what yarn and hook they used when posting pictures of their projects. Here is the current one.

My own personal favourite for small stuff is 16/1 linen or 16/2 cotton with a hook in the 0,6-1,25mm range, depending of what I'm making. The linen is especcially nice since it drapes well once it's been broken in.

 

I recently crocheted a couple tops and shorts from Sewrella Yarn sock weight mini skeins. It is on the more expensive side though. I got them for a different project, but decided to use them anyway. I actually really like it for MSD clothing since it's not too bulky. It's the smallest yarn I've worked with so far, but I'd definitely make more MSD clothes with this yarn. I too have to take breaks otherwise my hands start to hurt. I didn't think the yarn was too difficult to work with, even though it was quite thin for what I'm used to.

Here's some pics of what I've made with Sewrella sock minis (using a 2.25mm hook):
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I've also used Caron simply soft and We Are Knitters pima cotton to make SD clothes. I like them, but Sewrella Yarn has been my favorite. Sewrella only does seasonal colors however. But the mini skein tonal sets are very nice.

 

I've been playing around with different materials and hooks and so far my experience is this...

Embroidery thread could give me a good weave, but I need smaller hooks (I was using a 2.5mm, and it was a very loose weave).

Super fine, or sock yarn, with a 2.5 or 3mm hook works up wonderfully, and won't look too chunky on an MSD size doll. When I'm done with the vest I'm making for my boy, I'll post some pictures.

Wool and wool blends can feel scratchier and stiffer.

For a lightweight feel, and something that feels super soft against your skin, you can look for bamboo and bamboo linen blends. Some cottons can be really soft, but some can also be really stiff.

Alpaca can be super soft, and is a good alternative if you're allergic to wool.

I've found decent pricing at Hobbii (I think they're based in Europe?) - and a better selection of colors and materials than Michaels. Last time I bought anything from them was pre-2020, so I'm not sure what their shipping is like anymore, but their prices are still reasonable. I don't have any local Yarn stores near me anymore, sadly. The only downside to shopping online is not being able to feel the yarn before purchasing.

 

I've found silk and rayon (they call it "milk silk" or "ice silk") reasonably priced at Temu.

 

I’ve been toying a lot with crocheting in minifee scale, for reference. Right now I’m using knitpicks alpaca cloud lace weight yarn and a 1.25mm hook. I do have to take a lot of hand breaks though! This particular yarn does split a bit, but I think the big info here is that laceweight is probably the closest I can find to equivalent of worsted in human scale, aside from maybe 2 strands of embroidery floss, which requires a lot of prep to work with.