If you've never worked with this stuff before, be aware that it can be messy as hell.
You'll need full coverage disposable coveralls, goggles, gloves and a good respirator....and shoe covers/or old shoes you can throw away.
A good masking job on anything in the van you don't want foam stuck to.
Here's a link to another brand that has pretty good info as well.
Another option is to see if you have a professional near you and see what it costs to have it done for you. You would still need to do the masking job yourself to keep the foam away from where you don't want it.
That said, if done properly it would be a very good option.
Personally, though, ya can't really beat using Polyiso sheets for DIY ease and cost effectiveness.