Difficult spots after zenithal or white prime?

[dire stump]

I've been struggling with this since I started painting. How do you deal with spots that are upwards, but still under a shoulder pad etc? Space marines neck area, under pads, necron insides and so on.
Especially if I use speedpaints, and cant manage my brush in the tight spots. If i dilute so that it runs to them, it really wont colour it enough.
If I paint from black prime, then ofc its not a problem since it can just stay black.

Things i've done so far:
-blast some darker basepaint with airbrush in those spots -> ruins the zenithal and i need to clean it up
-subassemblies -> don't like to do it all the time, and it's not really speedpainting anymore

Okay this space marine isn't that hard since all of that will be armour color. But what if I want to make light coloured helmet + shoulders, and my fat brush reaching those spots will touch my prehighlights?

[wary solar]

Sounds like your main solution is to get a smaller brush like a 1 or 0 and delicately try painting the base color in there (or white for zenithal), aside from trying to hit those spots with airbrush zenithal coat (they seem to be in line of sight from the picture angle).

[blazing gate]

I have 3 ways of dealing with those, and generally you are spot on with what you've done:

• subassembly: blue tack those pieces for zenithal, then take them away, paint
• base color whole mini and don't do a zenithal, this will end up with more "artsy" (or... "non-'eavy-metal)" look if you continue with building up color from say purple shadows, those places then end up almost not painted (because they are in the shadow), but the shadow color is there
• dilute paint and in a wash-like fashion apply paint there (I paint those spots first usually)

it also all depends on the look you want to achieve

truth be told.... just try different things few times and settle on something that looks good/ok for you and you are willing to do it on the whole army.

[fast terrace]

Liquid Mask. The end.

Mask the areas you don't want to paint. Then don't worry no matter how sloppy your technique.

Apply mask with rubber clay sculpting tool

[dire stump]

Gotta try liquid mask, thanks.
The size of the brush doesnt matter since some of the places are out of los and cant reach even with a single hair brush.