Again different people will give you slightly different methods, some don't wash the print after the fix, they just go straight into the selenium.
I use Kodak selenium toner. I have dilutions that I keep in a two different bottles. One is 1:9, and the other is 1:20.
They are both reusable after toneing. Simply pour the solution back into the bottle and store it.
Selenium toner changes the silver in the paper to silver selenuim (I believe) but what it does is make the print more archival since this new compound is more hardy than just the silver.
Some papers will also react to the selenium by changing color. Warm tone papers react to change color better than ordinary papers. If you use say Ilford MG FB Warmtone, with a warm tone developer like Zonal Pro Warmtone developer and afterwards selenium tone you will get a rich warm tone. If you normal Ilford MG FB you will get very little color change. If you ILford MG FB Warmtone with say LDP 1:8 you will get a slightly purpleish warm print. There a many variation, depending on the paper and developer.
My process is fix for five minutes in running water, Hypo clearing agent for 3 minutes, with agitation, selenium tone for about 5 minutes at 1:9 then wash again for five mintes, them 3 minutes hypoclearing agent then into the archival washer for about 1 1/2 hours. This is all with fiber paper.
Also selenium is nasty stuff. Use gloves, and I cover the tray with a piece of plexiglas to keep the fumes down.
Hope this helps.