Can this be used in the same way as Humbrol Matt Cote i.e. to create a dull finish?
Also, does it need warming up/thinning prior to use?

The X-21 is a Flattening Agent. Add it to Gloss paint to make it a Flat Paint.

WAIT!

for the love of styrene dont paint or spray it on a kit!!

It is a flattening base to add to gloss paint. If you use it straight on a kit it dries white and chalky.

Luckily I tried it on some spare parts first.. in the bad old days before the internet...

Mike

you can add it to Tamiya's Clear paint. don't know the number offhand.. but it makes a great dullcote.

Ive heard that because of its whitening properties, it actually works well being sprayed on winter vehicles giving a frosted-like appearance. Havent tried this myself so cant confirm this, but its sounds plausable.
As the others have said .... its is not the same as matt cote.

Ill try that. the humbrol matt cote isnt in my local model shop (not a lot is) and I dont wanna wait for mail order.

any idea of % mix on that?

I'm sure it's on the Label

Well, on my bottle of X-21 the only text in English, German an French are some general warnings ("use in well ventilated room" and this kind of stuff). Instructions for use are only in Japanese...

Among various Japanese letters I don't understand, there is "30%" in one place and "10%' in other. Probably these are suggested amounts to add to gloss paint to get various results (flat and semi-gloss maybe?...).

Rgds,
Pawel

Great stuff I use in all the paint I add two to three drops in the mixing bottle!
Works great with what I have tried Vallejo ,Polly scale, Tamiya real flats the paint!!