Just reporting back on my use of the Eastwood rubberized undercoating.
Summary – works well; messy to apply, but not horribly so; figure on at least four cans.
The longer version:
I cleaned carefully (as described above) and then put on Rustoleum 'rusty metal' primer. My car didn't have any rust per se (Texas car) so I didn't have to resort to the POR neutralizer except for a few spots. I then used Rustoleum paint over the primer, allowing a couple of days between coats. I wanted to make sure that the paint coats got really dry since I would be putting a rubberized coating on top of the paint.
Applying the Eastwood rubberized undercoating from the spray cans was pretty easy with some provisos:
Get a Harbor Freight clear face shield for three bucks and put a bandana over your hair. That way you can get up inside the fenderwells to make sure that everything gets covered. I also had a set of $6 Pepboys used mechanic's coveralls and throw away gloves. Even then, I got some spots of black undercoating on me. Despite my insistence to Mrs. Lokki that this was a good thing since I'd never rust in those places, it was a pain to get off.
This is also a good place to point out that a good masking job and some well placed and applied drop cloths are your friends. The stuff IS hard to get off the car too, after it’s applied. Acetone works, but should be used carefully since the undercoating isn’t the only thing that acetone dissolves.
Figure on a full can for each fenderwell, if you’re anything like me. By the time I was comfortable that everything had been fully covered, there wasn’t enough left to be worth saving for another fenderwell. Additionally I suspect (but don’t know) that the likelihood of the nozzle clogging is pretty high, so you could end up with any unused portion stranded inside the can unobtainable.
If I had to do it again, I’d put a brighter color on between the primer and the undercoating. The reasoning is that when you use a dark color, it’s hard to see enough contrast to be sure that the undercoating is fully covering the paint everywhere. Remember that it’s dark up in the fenderwell, even with good lighting particularly when you’re wearing a faceshield and that face shield is getting covered with splatters of liquid rubber. If you’re painting black undercoating over black paint you’re definitely going to miss a few places, and it’s no fun to get all dressed up again and go back in to retouch. Better to make sure you get it all the first time and a bright color to cover will help. Nobody’s going to see it anyway after the undercoating is applied.
At a local hardware store, I saw a can of 3M undercoating that appeared to be a similar product. The cans were smaller but considerably cheaper, particularly since you’re not paying shipment on them.
Lastly, think about loosening the pittman arm and steering box bolts enough to be able to cover the bolt heads with tape. Otherwise when you eventually have to remove those bolts someday, you’ll have to clean the bolt heads to get a wrench on them, and that will break the continuity of the undercoat. If the bolts and washers are moved away and taped, they’ll go back on ON TOP of the undercoating rather than under it.