Hi dan, what a lot of people do is to give the model a coat of gloss varnish after the paint is dry ,then after that is dry apply the
decals , the smooth surface helps avoid any 'silvering' of the decal , caused by tiny air bubbles getting trapped underneath if the surface is too rough ie. matt finish. Then when the
decals are dry ,you can apply a final surface finish ,whether its matt,gloss or satin ,whatever, this also helps to seal in the
decals. If you want to do any weathering too then now is a good time, and if you want, another coat of the final finish after. As for the manufacturer,theres loads,it all depends which you can get, but a few good varnishes are - Vallejo, Microscale , Xtracrylix , or if you want enamel then humbrol clearcote . all available in matt and gloss of course. If you wanted the microscale stuff then its available from johns own shop on here, just click on the link at the top of the page. hope this helps a little , cheers tony