All the concerns over "pencil" sanding tools, edges, cracks, reveals, door jambs, blah, blah, fuckin blah. Scotchbite. Yeah, I said it. "Scuff Pad" in body shop lingo. Red and grey are the standards, green n white are "specials" in general. The thing to remember, and even the most seasoned of finish guys miss it now and then, don't push so damn hard. Let the pad do the work. Push hard and it literally "melts",or more accurate, bonds itself together from that localized heat and stops working. All the consternation of sanding into a reveal (like on a 30s body) usually has the finisher doing the "tootsie roll" with sandpaper of varied grits over the course of the job. The reward is the wobbly grooves under the raised reveals that you see from 30+ feet away. Makes me say "...forever rookie..." when I see it. Then there's the old venerable red rubber block, you know the one with the nails in the fold that holds the paper, right? Hard to forget the size when you see the groove below the reveal, also from 30' away, and often runs the full length of the door or indeed the whole car. "Ok Highlander, shut up and get to it!" is likely in your head now, right? So your body work is done and the primer is so nice you almost don't want to paint it, and here comes the worry, "I gotta make sure I sand in the groove/reveal/etc...". 1st thing you do is take a red pad and gently scuff it. Don't dig at it, don't melt it red, don't make a tool shaped like it, just wipe it easy like you would with a solvent rag. Trust me, it's enough. Once done you can block sand the surface to perfect and NEVER see the groove, never see the block line from sanding along it's length, and best of all it's EASY. I like EASY, I'm lazy like that. Is it reliable? Will the paint stay? I have cars over 20 years old in lacquer and urethane, haven't peeled yet. Mixing filler with glaze? Abso-fuckin-lutely. Main reason for me is multiple fills. The hardness changes and the new is too soft, the feather edge becomes stubborn, so it's wait or improvize. I don't care if it's $100/gal mud that washes your dishes for you, the differing hardness in multiple coats basically sucks and requires 110% attention and discipline, but remember, I'm lazy like that and usually just don't want to wait for each layer to get the same hardness. Mixed with Metalglaze or Icing, a "taa-daa"moment for those final skim or finish coats. So my invention? Conversation with like-minded folk and sharing ideas. Scuff pad 1st, even on a refinish deal, just scuff out those jambs, reveals, grooves, any of it before you plug in the DA. Now, there is a cross-over product that might work for those little holes or deep chips that would be misery to feather, easier to fill. Mrs Highlander does nails and acrylic tips. She uses a powder and monomer that hardens the fill material in minutes. Applies with a simple brush, would be great for such things. At the end of the day we need to keep a lot of this shit in perspective. Sometimes the answer is a cup of coffee away and easier than we think. Then again, all the stuff I work on is ancient technology to begin with so perhaps re-inventing the wheel doesn't occur to me very often. Merry Christmas, Happy New Year, make it shine.