Tamiya M48A3 advice

The US Army also used a fairly glossy dark olive color during Vietnam so a little shine on a tank from this era is not in error.

I agree with the previouse answers . Just put a coat of matt over the finished glossed area .

what Bronto said.  Some armor builders don't bother with the clear coat if the decals don't have a lot of film around them, but American AFVs have all those small designation letters on the hull and the clear film around them just promotes silvering on matte paint surfaces.

Yes, the process for adding decals is the same for armor as it is for aircraft