Leather gloves? The bulk might not be helpful though. BBQ tongs?

Unfortunately, leather gloves don't help. See, e.g., here. These are heavy leather gloves sold for handling cacti, but they specifically note "DO NOT use these gloves or any gloves to handle Cholla & Prickly Pear. Prickly Pear cacti not only have spines but have thousands of small whiskers called glochids that will get into most materials and are quite painful when transferred to your skin or eyes."

Tongs don't help tryiing to pull out, for example, knotweed: you need to very tightly grasp something that's a few millimeters thick, and in a confined area. I would need something pretty fine-tipped (say, the width of an index finger) that also manages to have strong grasping force. What makes the last part tricky is that it would have to be at least a foot, closer to 18" long so I can reach down to near soil level, so the lever principle is working against me.

I aggree with scot. I use a maggazine or news paper. Leather gloves are made of skin. and the let glocids in just like my hands and then the gloves are RUINED. I use a long hemostat for weeding around a cactus. I am lucky that my fater in law was a surgion and had many old doctor tools that I absconded with.