Should I first undercoat exterior cladding on my house or just use a 1 coat paint?

The cladding is like a tile (made of ??) and has a timber pattern pressed into it on the front side.Over the years it has already been painted several times and in places the paint is peeling-especially as it is on the weather side.I have waterblasted as much as poss and have started to scrape and remove with a wire wheel on my drill.If I am to use an undercoat -what sort????????Should I first undercoat exterior cladding on my house or just use a 1 coat paint?
There's a brand called ';Kilz'; that has paint for just about any application you can think of, and they're prices are reasonable.

computer security