Harm in applying Future over Dullcote?

Yes Future is very durable, even when flattened to mat finish

Don't know about dullcote specifically, never used it, but trying to remove any varnish will damage or destroy the finish you are trying to protect.

Make sure the model is clean first before applying future with Tamiya xf22 flatting agent added to it as below. Don't apply to the cockpit glass btw...

Google " The complete future " from Swannys models for all you need to know about future.

Consider mounting your model to a base as well?

As stated, you cannot remove the dull coat. But you don't have to. Simply spray your Future/flat base mix right over it.

For future reference, to the best of my knowledge rubbing alcohol won't remove dull coat. Dull Coat is a lacquer and would require lacquer thinner to remove. Or maybe a good soak in Simple Green.

I'll add that flat finishes are typically more delicate than gloss ones once dry. The crystaline structure of the flat finish can be marred with abrasions or impacts, making the product look like white scratches or small glossy marks where it's been rubbed. It's still there, it's simply damaged. Any flat finish will do this to some degree, be it paint or clear coats. Tamiya flat paints are reallly bad about it in my experience, scratching at the slightest threat of a cause.

My last 3 builds have been sealed with Acryl Clear Flat and Semi-Gloss thinned with Alcohol. Boy am I happy, I don't know why I didn't try this before.

As for your question, I don't think Dullcote (my favorite before discovering Acryl Flat via airbrush) is removable. I don't feel comfortable in the long run with Future, but that's me.

Thanks all for the info. I was supprised to read (somewhere?) that the dullcote would come off with alchohol. But it makes sense that it would be more difficult then that. I remember doing a glossy enamel coating over some model kits several years ago and didn't have any problem with it at all, so it's good to understand that flats aren't as strong.

Now to clean up the scratched bits and start looking for some future.

You could simply spray your Future mix right over the scratched flat coat. It'll fill and hide just fine. Unless the scratch is through the paint, ofcourse.