So I've had my prismacolor pencils for a while now and a colorless blender pencil but didn't really know what to do with them. Now after watching some youtube videos and tutorials I think I got the hang of it so today I went to Michael's and bought the Mona Liza Odorless Paint Thinner but after reading the label warnings I got scared and decided not to use it. I then remembered someone said they used baby oil so I tried to find some around the house with no such luck...while looking for the baby oil I found this product called Blue Goo skin softener that I had bought a year ago at wal-mart and never used it...and wondered if it would do the trick and it sure did. Here are some images that I used with the Blue Goo and the prismacolor pencils. The only one used with Odorless Paint Thinner is the yellow present at the top right corner. I think you could probably use vaseline also. I didn't really use that much just barely dipped the corner of the blending stump.
This second picture is the result of my colorless blender and prismacolor pencils.