Body shop guru needed

[bmgm3]

I'm currently striping my 1990 BMW E30 M3 for restoration.It will be a complete bare shell job.My question is,what is the best way to paint and protect the shell,especially the underside. I've noticed during the strip-down that the underseal looks fine,only for you to remove a small chuck and find a nice rust patch underneath.I'm planning on having the car blast cleaned,so what would be the best way to protect the underside ? I've been told by several people to underseal the car,only to have an equal number say don't. I guess all new cars still have some kinda underseal,so maybe its improved over the years. If anyone can help .I'm all ears.

Thanks

[wildoliver]

Old engine oil for sills and cavities, and schutz for underside.

[hal 1]

After blast cleaning make sure everything has a coat of etch primer preferably zinc based, personally I'd waxoyl sills and other cavity's
good luck.

[byron]

hi i would not use engine oil as it doesnt dry so when you want it painted it causes all sorts of probelms ,use an etch primer first then when the cars painted use a anti stone chip on the under side and wax oil

[wildoliver]

I very rarely come across people wanting the inside of box sections and sills painting.

And the non drying properties are what makes it work because it creeps, seen too many cars that have rotted out with waxoyl and ziebart over the years.

[hal 1]

yes i see what you mean, would be difficult painting inner sills

Why 'old' engine oil? must be full of all sorts of cr*p why not new?