The way I do it is to use a heavy fixed lead with a very short hooklength (3 inches) if need be. You need a very sharp hook, obviously, and a bait they cannot pull off. A good firm boilie or if you use a pellet pull on a plastic caster before you put in the boilie stop. They find it much harder to pull it off then because the tension on the hair caused by the plastic caster stops the stop from working loose. Another way is to superglue the bait to the hair. Don't worry, superglue doesn't put them off. I have covered the pellet in superglue before when nuisance fish are a pain and they still take it! A plastic bait is another option.
With backleads, I use a second lead, at least 3 feet above the first one which is held in place with rubber stops.
Pretty it ain't but it is very effective when weed is a real pain.
The key is the fixed lead, short hooklength, tough bait and sharp hook.
Be careful to set your clutch lose or use a centrepin.
You will lose your rod otherwise!