Hey there, Nelson! It sounds like you've been doing your homework and we'd be happy to tell you all about our undercoating process and what will work best or your truck. Give the store a call or stop in sometime when you're able to.
It depends if you pay to have the plugs removed and then sprayed. If you go the lost cost Ziebart they don't. If you are talking the black textured finish inside the box? There is no rust proof sprayed there. And they like to keep 2" away from any painted surface. So they don't have to clean up the paint. Which means the lips on your wheel walls aren't done either. I would go somewhere and get the oil mix instead of Ziebart. Or at least that is what I will do on the next vehicle.
1- no it is done with a yellow waxy spray. 2- the drain holes being plugged aren't usually an issue if they are it's an easy fix
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