We use rotational grazing here - ponies follow sheep, sheep follow cattle. We pick up the pony poo, and rest the ground after the ponies.
With the sheep we usually worm any yearlings as they come into their second spring, otherwise I now only worm if I see a problem, which is usually something like one older ewe after a hard summer rearing twins, two lambs and maybe one of the sheep wethers. (Out of 12 adults and approx 12 lambs.)
I am trying to get plaintain established in the sward in some of the fields, which is the only natural wormer likely to grow on our exposed clay site. But we were overstocked for a few years so it will take a year or two more of grazing less hard to get it established in the grazing fields, I think. It grows fine where nothing grazes...
We also use minerals - everyone has a himalayan salt lick available at all times, the sheep also have a non-soya mineral lick most of the time unless they are sharing with the ponies for a week or two, and we now use Jonathan Guy's mineral drench once a year. Keeping the minerals right helps the sheep fight worms and other parasites.