Recently we added another "arsenal" to our auto body product line. Sometimes after hours, days, and even months of sanding filler and primer, you start to see "things". It makes you feel as if you are a shipwrecked sailor. You know the feeling, you're fine-tuning a dent that you had hit with the stud welder, laid some thin layers of filler over, and sanded diligently in between. All while running your hand along the panel to feel for low spots... before your eyes new low spots seem to "appear" and the original dent you started with seems to get even bigger!
I've found that using a small bit of guide coat over a area you are filling or priming is very helpful in eliminating the doubts of a phantom low spot. Especially one that might show itself only after the car is painted and shiny. This is especially true for someone like myself that is a "novice" in the auto body field.
Below I took some pictures of one of the bedsides on my 1981 VW Rabbit Pickup project. This truck originally had dealer installed bed rails that were used and abused to the max! So much so, that they had even pulled some of the threaded inserts out of the bed sides. Once I removed the bed rails, the bedsides looked similar to the water in your swimming pool after the kids have been playing in it for hours! Because I am going with a "clean" look for the truck, I will not be running bed rails in the future. This means I won't be able to hide the "waves" and oblong holes with the bed rail feet. So I began by using our hammer and dolly set to smooth out the major dents and high spots around the mounting holes. I then welded up the old mounting holes. I was then left with some smaller "waves" and low spots (and a couple pin holes in the welds), This is where the "sanding, filling, sanding more, filing more, sanding again" process occurred.
Above you can see my first layer of Rage Extreme filler has been laid down. This Evercoat product is very user friendly. It is the first "pinhole free" body filler of it's kind according to them. I was a little skeptical, but after using it numerous spots on the body of this "field find", I had quickly forgotten about my glazing putty. I then blocked the area to 320 and I still felt like there was a small low spot right near the back end of the bedside. I sprayed the black guide coat (it also comes in TAN for those of you using a dark colored filler, or black primer) over the entire top of the bedside. I've found doing a extremely light coat over the area, holding the can about 12" away works best. You can see in the last picture it looks like a light bit of dust over the top of the beside.
You can see in the first picture the sanding process halfway through. As you sand lightly, the majority of the guide coat sands off quite quickly. You will notice that low spots will leave behind the guide coat and pretty much outline the remaining low spot. In the second picture you can see as I had suspected, a noteworthy low spot. It is right where one of the mangled mounting holes for the bed rails was. I even took a picture of this area before I started the guide coat process (last picture in the series). Following this, I reapplied another concentrated coat of filler over the dent, block sanded to 320 again, and repeated the guide coat process. This eliminated the worries I had of having a the tops of the bedsides all wavy. I will surely be using the guide coat quite a bit when I put the body in primer next week!