Gasket advice please......

RTV is for your bath....

I use small acid brushes, sold for applying flux for tinning solder, for application of almost any sealant.

They do tend to drop bristles and are often not stiff enough for applying a thin layer of a thick sealant.

So, I first crimp the metal that is pinched around the bristles with an electrical crimping pliers. This holds the bristles fast. Then I use a scissors to cut the bristles shorter to stiffen them so I can apply a minimal layer of sealant

I put it on thin, keeping it just below the inside line of the case. When you put the two cases together it fills that space easily. Yes I ve seen
over generous applications and the Big Squeezeout. Tsk tsk.