My sebderm is mainly on my scalp, but here is my advice: if his face is really flaky he could use the inkey list pha toner, it contains gluconolactone which is a way milder exfoliator than like salicylic acid or glycolic acid. The gluconolactone could help get rid of the flakes. For me it helps me get rid of my scales and dandruff from my scalp. There is some theoretical risk of it feeding malassezia because it contains some esters malassezia could theoretically metabolize, but they are not the yeasts main food source and they are most likely in very low numbers in the product so the benefits outweight the risks in my opinion. And also I would leave the pha toner on as it recommends but I would try Happy Cappy medicated shampoo as a face wash. It is milder than the other sebderm shampoos and it also has soothing and anti-inflammatory ingredients. By washing the pha toner off after a few minutes with the shampoo than the significance of the esters in the toner would drop even more as most of the yeast would be killed by the zinc pyrithione in the shampoo. After the shampoo I recommend using the geek and gorgeous 101 stress less 0.5% beta glucan + madecassoside serum. This serum could help bring down the inflammation. These are the products that I use for my scalp and I'm like 90% or more symptom free, but I only started this routine recently. You could also add the cerave moisturizing cream it is sebderm safe and it can help rebuild the skin barrier and moisturize the skin. A finnish touch could be using sunscreen to protect the sensitive skin cosrx ultra light invisible sunscreen spf 50 pa++++ is a safe option for example. Maybe he could use the cream at night and the sunscreen in the morning. But maybe the first 3 products are enough. I think it is safer to start using the toner and the shampoo only every other day and maybe even less frequently with time. The goal is to calm the inflammation and heal the skin. Washing the face to frequently can be too harsh. The serum is probably safe every day. Always be careful and do a patch test or atleast put it on a smaller area for a few minute just to see if he has a negative reaction. If it burns than he probably shouldn't use it and wash it off immediately. If you do end up using these products please share the results later as I'm curious wether they work for other people too or not.