Yes Rod, After guide coat blocking a number of times, I use a clean clean clean, such as a Windex spray bottle, and I apply a few squirts of clean water, then I wipe the panel down with, for example a clean dry dish towel which applies the water evenly. Kind of like the pavement on a street after a light rain at night giving a bit of a shimmer. Then shine a light from behind you....using a lamp, and the panel will shine like it has a coat of clear coat on it. This technique will expose any waves, nicks, or low spots you may have missed using your guide coats. You are aware of the definition of a guide coat being a light mist of a fast drying spray bomb paint which is compatible with your primer surfacer.....so you do not develop any lift, and that the mist will adhere on the low spots and can be painted over with the next coat of primer surfacer. Again, using the longest block that you can, given the panel, you will be able to see the low spots by the mist spray that is left behind. I use my eye, my feel of the hand, and the guide coats, primarily. My final test is the water mist where I am looking to confirm that I have the panel as true to whatever ambient light the car will be exposed to....from bright sun, to a night time street light. Believe me, the water trick will tell the truth on body work. So far, no complaints.....soooooo far. Check out the YouTube channels on blocking. Now is the time to do it....especially with all of your hard work and the $400.00 plus per gallon base coat....and then add the clear coat cost. Hope these thoughts were helpful. Looking forward to your final photo in the "sun." Best. Old Dart 66.