HINT: Basting tape is your friend, pins are a pain and take longer. I do use pins for major seams but not for those tiny hems. I also use it to place trims before sewing.
I've made piles of Barbie clothes and my easy solution for the hemming is
1/4 inch basting tape......(note: check the labeling, basting tape and craft tape are packaged almost identically, the craft tape will gum up your needle)...lay the tape on the wrong side edge and fold over the 1/4 inch and run a seam for the hem or fold it once more. I often use a decorative stitch that will somewhat overlap the raw turned edge. I've done this for lots of little Barbie outfits and they hold up just fine. For most little girls quantity edges out time consuming designer finishes. I also, depending on the age of the child, cut the small Velcro dots in quarters, use a little basting tape to place them on the garment and then do some quick "X" stitches to hold them down. For older children I use snaps and buttons. Even where buttons are called for I'll put either Velcro or a snap and sew the little button on top. Easier and more stable than a teeeeeeeeeeny little buttonhole. I found a web site that sold tiny zippers for Barbie clothes a long time ago and bought a huge package that I still haven't worked through after 15 years. Once again, basting tape is your friend.
If something is really ravely I lay the cut piece flat on stabilizer and serge what will be raw edges before I sew it up. I still use the basting tape trick on those. Much easier than trying to pin. I also use that clear plastic sort of "U" shaped foot on my machine for the tiny sleeves and pant legs. It's shorter so it fits inside the loop better.
The one thing that I have done is lay the uncut tissue pattern on iron on interfacing and then cut them out. I have patterns that are over 20 years old and still remain in very usable condition.
Val