Rust check undercoating, DIY vs. paying to get done Options

[K-ESD]

What is the big science behind undercoating a car? Winter is coming and my celica is gonna have to get thru it.

I'm definetly undercoating it with rustcheck. Now is it worth it to get it done "professionaly" or is it just something anyone can do? Is the rustcheck they sell in stores the same stuff they use at the shops? What do i need to do besides spray everything of the undercariage and engine bay?

Thanks

[K-ESD]

well after examining my car (which the previous owner had rustchecked) i found that stuff everywhere !
Under the hood, in every little corner of the engine bay, everywhere inside of the body shell, fenders, quarter panels, doors. So i'm getting a pretty good idea of where to spray.

I would suggest rustcheck over rubberized undercoating, eventho i have no experience with rubberized undercoating, i know how well rustcheck worked on my celi.

My car is a 94 and has been driven in every crappy salty winter since. The only place it rust was at the corner of the brake light on the hatch (a place where they didn't spray). Last time it was rustchecked was 4 years ago. Cars that age around here are usualy rotted out. I did forget to mention i hate winter