If you are toning for archival reasons, any paper combination and developer combination will work.
If you are toning for a color shift, you probably want to use a warmtone paper. You will also get added results with a warmtone developer.
Usually RC paper doesn't tone as well as fiber.
Color changes differ with each paper, developer, and time and dilution in the toner.
Save the selenium toner and you can reuse it indefinately however the times usually will increase.
I use a 1:9 and a 1:20 dilution depending on the desired results.
Hope this helps,