Many of us work alone. We put a stick against the brake pedal and seat or use a mirror or see a red reflection. We try to think outside the bottle. Anyway, sounds like you need to do some metal surface clean up and rewiring. Should take care of a lot of issues. If not, let us know. 24/7/366.
Everyone should have an ice pick voltage tester. It's much better than a meter for most things. Simple, no batteries, no settings, no reading anything, one handed, fast visual result, cheap. First thing is to see if the component is getting voltage. This will identify/eliminate bad switch, bad component, bad wiring, blown fuse, miswiring. Ground is not the first test, it's harder to find ground issues. After you see voltage at the component or it's contacts, then you proceed to other causes. Which is usually ground. Then you can use the ice pick backwards.
For a no light issue, It is a good idea to begin by checking the offending bulb at the battery .....or bulb swap.
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