The Epsom Salt bath does work good for treating psoriasis as I have Psoriasis and take an Epsom Salt Bath 2 to 3 times per week.
The Epsom Salt Bath helps to remove skin cells and helps get rid of the itching associated with my Psoriasis.
An oatmeal bath or other sea salt bath can help with the Psoriasis as well and I sometimes alternate between taking a Epsom Salt Bath and a Oatmeal Bath and they both work good for treating the Psoriasis and makes me feel much better.
So I would recommend doing what I do and on some days take a 30 minute Epsom Salt Bath and then on other days take an Oatmeal Bath and you can soak in the Oatmeal Bath longer than you can in Epsom Salt.
But they both work great for treating Psoriasis.