Gauge cluster lights far too dim.

[Greenlee]

Here is mine with just LED's, no paint. It was dim before I swapped in the LED's. Honestly, I don't think the paint is necessary. If mine were any brighter it would be distracting.

[Dead Parrot]

Not sure how complete your 'fiddling with the knob' was but the gauge light brightness part of the headlight switch is basically a coil of wire over which a contact rotates. It is very common for that coil or contact to get dirty or fuzzy with oil, bugs, dust, and worse. This can prevent full brightness. Since pulling the headlight switch is much easier then pulling the gauge cluster, I would check the switch first. You should be able to jumper around the dimmer to give full voltage to the lights. Then you can decide if you need still more brightness.

Make sure all your bulbs are good. Some seem to have more effect on gauge brightness then others.