[Geek44]

I found that the method of only applying gloss to the area where the decal will go worked fine on my tank because subsequent weathering rendered the area matt again. Well...not strictly matt, more of a matt/satin but that was okay. Having learned to observe earth moving equipment as an aid to modelling, I've found that any vehicle has matt parts, satin parts and even some glossy areas...it's the mixture that keeps things interesting. After the decals had set, I then applied a coat of gloss over them to seal them in and impart that 'painted on' look that we're after.
Aircraft are different as I said and when I model them, I try for a satin finish for the most part. I would gloss the whole model, apply the decals and then gloss again for the above reason. I weather my aircraft quite differently to my vehicles...they get dirty differently and if possible, they're kept cleaner. A dirty aircraft suffers performance problems that can mean the difference between life and death. I read stories of the Luftwaffe enlisting the help of local school kids to bring their parents furniture polish to the airfields after school to help gloss up their fighter aircraft.
I always use Tamiya gloss acrylic. It's tough and fingerprint resistant.
Interested to know more about the diluted white glue method WR. I always found white glue peels off if applied thinly enough.
Peace.