I’ve never used toobies but it’s the same principle as the slinkies I have used. Slinkies are essentially parachute cord without the core, with round shot placed in them and sealed. It is hard to add or subtract shot, so you must make them up with different numbers of shot for different weights. Toobies are the same thing, but use a plastic tube instead of parachute cord to hold the shot. I believe the shot can be removed or added as needed.
I don’t use either at this time, although I do find it useful to clamp my shot on the tag end of my blood knot when using multiple shot. I tie an overhand knot at the end of the tag so the shot doesn’t slide off too easily. I lose a lot more shot than flies, which is okay by me. Maybe if I had someone across the stream to shag my line when I got stuck on the bottom I would feel differently. You’re the first fisherman I’ve ever heard of that fishes with a caddy!