Cleanest method I have found:
- Mount dry tyre on dry rim. (Make sure its to the edge all the way around)
- Pull tyre bead from the rim at the top and run a bead of glue (has to the thin stuff) on the rim and place the bead back in the position you want it.
- Tyre bead forces the glue around the rim so it will be instantly glued in place.. (you may need another small blob on the other side if its missed any)
- Leave it to dry whilst doing the other rim and then repeat for the other side.
This way, you dont get the glue inside the return edge of the tyre and its fairly true as you dont have to try to re-position the tyre whist the glue is drying.