Psoriasis flare-up on face - can I introduce new skin care routine? Help!

[BritabroadinAsia]

I was about to start a shiny new CH-style skin care regime but have suffered a big bad flare up of psoriasis on my face, which - apart from looking deeply unattractive - is now feeling tight, dry and itchy.

Am undergoing some light therapy on it this week, and have the cortisone cream to hand, although really don't want to do that unless completely necessary as my ageing skin doesn't need thinning any further!
At the moment I don't even want to wash my face, let alone try an acid toner....

So
a) any treatment recommendations from fellow psoriasis sufferers, please?

and

b) any words of wisdom from you lovely skin care gurus about suitable products for my otherwise combination skin, which I had fully intended to introduce to retinoids? Am sure I need to hold off for the moment, but if you have any good ideas about what to use in the meantime (DD's Cetaphil?) I would be v grateful.