I'm going to try dot filtering for the first time. My model is ready to go except that I don't know whether I should apply the decals before or after the dot filtering. These will be actual decals, not dry transfers, if that makes a difference.

IMO after; they will help blend the decals into the overall model. if you apply the decals after you filter they will look even more out of place.

Apply and seal the decals first. If you don't you, will have a weathered paint finish and bright, clean decals. You want to weather it all the same so the decals blend is and don't look like they were put on after the weathering.

1. Apply gloss varnish where the decals go
2. Apply decals using decal solution of your choice
3. Wait for the decals to fully dry
4. Apply matt or satin varnish over decals
5. Weather away!

IMHO all decalling should be done before any weathering to be done on a model.

HTH
Greg

Do it after decaling,but give them an acrylic sealer 1st.