Have u tried UV light treatments?
They 100% work for my DH- and he has psoriasis all over his body.
It clears it right up if he goes 3 x per week.
Big commitment.

The other thing he uses to keep it manageable is Elocon (sp?) cream.
It's a teeny tiny tube- so he can't cover all his psoriasis, but works on his face.

ETA- try the Elocon if you only have a bit of psoriasis.
The light treatment is harsh on the rest of your body.
DH is almost covered in it