I live alone, and when my psoriasis was at it's itchiest I could not reach my back to apply any topical treatments.
I found that taking a warm (not hot) bath with Oilatum or Oilatum Plus bath oil in the water helped to reduce the itching enough that I could fall asleep. I used double or triple the recommended amount in the water.
For the places I could reach, in the mornings I was using Exorex coal tar treatment, and my GP had prescribed Psoriderm lotion.
For the rest of the day and at night, I applied Doublebase Dayleve Gel. (I had tried possinbly every other moisturiser/emollient I could find). Some people report excellent results from Aveeno.
Lastly, something you could try is to take an antihistamine tablet - eg piriton. Your pharmacist might be able to help with advice. If you can still get the version of piriton that causes drowsiness, then that might help also.
Good luck.