Like a haggard drug addict, my 75 twin slider Panel van

Right, So im getting ready to insulate my van. I've read all the threads I could find on here, and elsewhere on the internet and this is how I think im going to do it.

Flashing Tape the inside of the panels. (the bare metal, as flashing tape is waterproof, so should hopefully stop condensation)
Then add Thermawrap, or Cellotex on top of that. (id probably stick it down with carpet tape)
And then add my ply wood outer layer held down with self tappers.

Does that seem like a logical way to do it? I've read so much about it, but it seemed that thats probably going to work best, and it should work for the roof too, I hope?

I'd do the floor afterwards, but im undecided on how I want to tackle that just yet. haha.

Has anyone had any bad experiences trying to do that, or shall i just go for it and hope it works out for the best.