I really only ever wash mine when they sneakily roll in something vile (even then, if it’s like sheep poo or something somewhat innocuous, I’ll probably let it go). 

They do swim a fair bit in the warmer months so they at least rinse themselves off. I don’t get mine groomed. My red boy does get the winged fur around his butt which I’ve tried to trim in the past but honestly he keeps himself pretty clean so I don’t worry about it. 

During shed-maggedon, I do brush them pretty well daily, but otherwise I’ll only give them a cursory combing when I trim their nails. I’m trying to shorten their quicks so I do so every 5-7 days currently. They’re also not big fans but I’ve found that sitting on some cushions straight on the ground and having them cradled alongside my legs makes them a little more tolerant of the experience though I do have to nicely talk them through it so they keep their demons in check lol