Take the animals off — completely
A worn paddock is worn because the grass never got a rest: roots grazed to nothing cannot feed the leaf, so bare patches spread and weeds move in. Seed thrown onto a paddock that is still being grazed is money scattered for the birds. Move the animals to another field or a sacrifice area and close the gate properly, because even a few nights a week of 'just the quiet pony' undoes the whole recovery. If you have only one field, fence off the worst half and reseed in rotation — a smaller area fully rested beats a whole field half rested.
Read the ground while it is empty
Walk the bare paddock and work out what you are actually fixing. Bare gateways and patches around feeders are compaction and traffic problems, not seed problems — those spots need the surface broken up and possibly gravel, or they will bald again whatever you sow. Weeds tell a story too: buttercups point to wet, sour ground, and dock and thistles thrive where grass is thin. Top or dig out the worst weeds before seeding so they do not seed themselves into your new grass, and if the field has failed repeatedly, a simple soil test tells you whether the ground needs feeding or its acidity correcting before grass will thrive in it again.
Harrow, seed and roll into a firm bed
Grass seed needs contact with soil, not a fluffy bed. Chain-harrow or lightly work the surface to open the sward and break up droppings and thatch, then broadcast a grass mixture suited to grazing animals — hard-wearing, low-growing species that tolerate close grazing rather than a lawn mix. Sow when the soil is moist and rain is expected, roll or tread the seed in firmly, and keep hooves and machinery off it afterwards. On gateways and repaired patches, a heavier hand with the seed pays, because those areas will take the punishment again the moment the field reopens.
Keep it closed until the grass can take it
The new sward is ready when it resists you: tug a handful of grass and it should hold in the ground rather than lifting away roots and all. Mow once, high, before grazing if it has grown rank, then graze lightly and briefly the first times — an hour or two, then off again — taking animals off while there is still leaf left, so mouths and hooves do not undo months of waiting in a single afternoon. Reopen the gateway end last if you can, and keep a feeder off the new ground so traffic spreads. Continue resting the paddock in rotation afterwards — a field that is grazed hard, rested, grazed hard, rested in turn stays thick, while one grazed continuously slides back to mud within a couple of seasons.
A resting paddock is easy to forget until someone opens the wrong gate, so set the work up in KinsLe's Care Teams — harrowing, seeding and the first high mow as dated jobs with names against them — and the closed field, and the reason it is closed, stays in front of everyone on the yard.