What did you use and why?  I just bought a trailer with a small DR, I want to eventualy insulate.  What lasts, is easy to cover, is not too expensive..... etc.

Thanks!

same here, foamboard.  But the stuff I used was pink.  

I just finished mine, ceiling & sides, with a from insulation board product that I found at Lowes that has a shinny metal finish (looks like alum.foil) and trimmed it out with the matching foil tape. It makes for a brighter inside until I can find the wall board that I want to use. This project was easy and fun. This insulation board is available in different thichknesses, so I picked the one that was the same depth as my support beams. I also "liquid nails" to help secure the product to the walls. Good luck! 

Another option is the foil faced bubble insulation that is available in rolls. For curved panels, it offers an easier installation than the rigid foam. It would not offer the same amount of "R" factor as the foam board, particularly the foil faced foam board previously mentioned.

The smallest heater will easily warm a dressing room or LQ. Having a minimal amount of insulation is necessary to prevent condensation on the metal surfaces. Obviously the more insulation that you install, the smaller the heat source you will need to provide for your comfort level.

Gard