I beleive that the best solution would be to use a wallpaper underlayment. It is approx $9/roll. It covers 56 square feet per roll. It may not seem economical, but it is.
Think of it this way. You need to prime your panels, maybe even twice because of the smoke build up on the walls. The smoke build up will bleed through. The primer is not cheap beacause you need a special primer ( I do not remember the name of the primer.)
Also once the panels are painted, it looks like panels. Where the wallpaper underlayment looks like drywall once it is up.
My wife and I went through the same problem and the underlayment has worked out beutifully.