In case you haven't seen it, Artist's Network has posted a free article by me on mounting oil paintings made on paper to board. It's some extra material that didn't make it into the print edition of my article on painting oil on paper that will appear in the March 2014 issue of The Artist's Magazine.
In the free article, I use a product called Beva film to mount the painting. This is a wonderful, heat-activated adhesive that comes in sheet form. It's a lot cleaner than using a product like Miracle Muck and, unlike Miracle Muck, it is reversible with heat.