I haven’t used Tamiya dull coat, so I can’t comment directly. I have seen a little white powder accumulation on SS car Z-channel when I got overzealous with Model Master Clear Flat and put down a wet coat. The talc or whatever they use tends to settle next to vertical details, on ladder stiles and rungs, or on grab irons, etc. The best way to avoid that is to use a couple of light passes, let it dry, and it it’s not flat enough, repeat the application. Also shake the can frequently to keep the particulate suspended and evenly mixed.  I never had that problem with Dullcote, and I don’t use acrylic flats because they cloud the paint color. I’ve never had enough powder accumulation to have to redo a car. The slight white residue I’ve seen can be covered during weathering, since it’s already in location that accumulate dirt and grime.

Sometimes Dullcote will cloud if it’s sprayed on a humid day. If it’s not too bad, spray Testors Universal Thinner on the car and let it day, If it’s bad, you can try brushing the thinner on with a wide flat brush and let it dry, but you risk ruining decals if they’re not well sealed.

Nelson Moyer

I’ve had sputtering rattle cans of Dullcoat ruin freight car finishes. I swore those off many years ago. I had used rattle cans of Model Master Clear Flat with good success before I set up a spray booth.

I now prefer to use the airbrush to spray Model Master Flat Clear Acryl with a few drop of the appropriate freight car color to add a chalky appearance to start the weathering process. The flat + drops of color also cuts the whiteness of decals. You can compare the before and after on a boxcar in this blog post.

http://designbuildop.hansmanns.org/2017/04/21/southern-pacific-a-50-5-automobile-box-car/

YMMV.

Eric Hansmann

Murfreesboro, TN

I neglected to mention that I don’t use Dullcote or Model Master rattle cans for clear coats, either gloss or flat. My experience was similar to Eric’s. The nozzle of Model Master Cans is nowhere close putting out a fine spray as Tamiya cans. I always use an airbrush for clear coats (gloss, semi-gloss, or flat), but even then, If I get too close or stay in one place too long, I sometimes get the white powder effect of raised details. Instead of trying to cover every nook and cranny in one coat, it’s best to apply multiple coats as needed with drying in between. My current practice is to lightly spray the whole model with clear flat and let it dry. Then I look for shiny places, and selectively spray a little more clear flat on those spots. There should be no need to respray the whole model if the first application was properly applied.

The ONLY rattle cans I use now are Tamiya and Krylon. Yes, Krylon. I paint simulated stainless steel betterment passenger cars with Krylon Flat Aluminum. Until Tru Color came along, it was the best of the ‘silver/aluminum/steel’ [paints for passenger cars. I made color ships of the Tru Color steel/aluminum colors, and it has very fine pigment, sprays without clogging the airbrush, and levels to a smooth, thin finish. I haven’t painted a car with Tru Color yet, but I think it’s as good or better than Krylon.

Nelson Moyer

I found out the hard way what apparently many other modelers already knew – using an alcohol/India ink solution over a freight car (or structure) previously sprayed with Dullcoat  would cause a reaction with the talc powder suspended in the Dullcoat which would result in the chalking/blushing mentioned.  I thought I had ruined a model I spent months on until it was pointed out that another coat of Dullcoat or Glosscoat would eliminate the problem.  Thankfully it was true.

Mark Rossiter