I decided to try some stuff I bought by accident (thinking it was paperclay) to cover the box with to give it a stone look.
Michelle from the blog "Michelles Mad world" which I follow mentioned she used this stuff to make her houses but leaves it for a while after making. I am far too impatient for that so left it little more than the hour it said on the packet after I had mixed it. It looked like this....
It was very soft but light and very sticky...so I immediately realised the rolling pin I had dug out from the drawer would be no good.
I coated my room box in PVA glue where I wanted the papier mache to go. This is what you do with paperclay....so I thought I'd do the same thing, which was just as well as as I progressed I realised it did not stick as well to places without PVA on. Then I just sort of smooshed the mixture into the corners and over the surfaces smoothing it with a finger or the pad of my thumb as I went. It did not cover evenly so I had to go back and fill in gaps where I could still see the foam board, but as I went on I decided I like the uneven texture...very rustic.
I covered the entire inside except the floor which will be floor boards and also the outside sides and top then using my paperclay stippling brush added a bit of texture. Here is what it looks like now.
I'm not sure how long it will take to dry but I made sure I kept a little bit of papier mache in a sealed container in case of cracks.