UVB home treatment-do's and don'ts

Hey folks, it seems more people are buying the UVB sun beds for use at home and I'm considering it myself as I'm not keen on the chemical route & creams just don't cut it for me. Ive searched a few Psoriasis forums for information on how to use the beds and what to do before and after a session but can't find a decent guide. Is there a source for this? Does the NHS advise on this? Can any forum members who are using or have used these units please advise on the following: How many seconds do you start on and whats the increments there after? Do you use a moisturiser after if so what one? Please give any other info you feel relevant. Looking forward to hearing from you. Many thanks Michael