My lionheads are mostly outside. They get a thorough combing through about once a week. Shavings and similar substrates are bad for getting tangled in longer fur. I use newspapers on the floor of hutches with hay in litter trays. If they are out on soil / grass etc, you may need to groom under their feet back more regularly as they do get filthy and matted quite quickly. All mine hate their big furry feet being combed through, but they really do need it.
Outside runs will need more shelter from rain as big fluffy coats don't do wet very well.
I do find that their coats vary a lot through the year. They can also moult a lot more as their coats are much thicker than indoor bunnies- so when they lose it, the pile of fur can be huge after a good grooming session. Summer coats are much easier to manage but winter coats make for really cuddly buns.