You need to keep on top of it and keep it well moisturised so the keratin doesn't harden and irritate the skin.
I'm slightly agnostic about keeping the hair short - I think it depends. I've kept coblet clipped skin close all his life (we've had him 20 years!). He has mallenders and sallenders - has had for most of those 20. He is also mud fever prone. So he is clipped skin close so I can medicate and manage. Last year I had a bad turn myself healthwise and he got quite a bit longer than I like (we normally clip every 4 - 6 weeks). The mud fever was a bit rampant under the feathers but the malleders / sallenders had actually been pushed away from the skin by the hair growth and the damage wasn't as bad as I feared. But we had to clip him skin close to find that!
I think the thing is you have to be able to get in there and manage it. If you can manage longer feathers taking the time to really get in there with comb and cream every day then you are fine. You really do have to get right up to the skin. Otherwise clip or cut back the feathers until you can - and loads of udder cream. Rub well in, every day and in 3 or 4 the deposits will have softened enough to come away without problems. Then just keep on top of it.
I wash with neutrogena t-gel shampoo, anything from every 3 days to once a week depending on how her legs are. I then apply pure aloe Vera gel in between times.
This works for us, I must have tried hundreds of lotions and potions before this, I think it is just trial and error finding what works for you. They got so bad last year I had to have the vet and use steroid creams etc.
I think that was partly bedding related as it coincided with using a new bedding and cleared up when I stopped using it and her skin was really greasy all over on that bedding. No idea why, I've known other people use that bedding fine, she was obviously just sensitive to it.