Do I need primer before I paint a patch of my wall?

Paint should be fine. Just be prepared for multiple coats.

If you are using a flat enamel then I would use a primer.

I don’t know the painting answer but I think it’s really cool that you had a female electrician!

I would use a primer on any virgin (unpainted) drywall or mud.

Thanks for the advice. What does primer do?

It has many uses, but in this particular case it would act as a sealer. Virgin drywall or mud is porous, and will suck up paint like a sponge. Once primed, your paint will sit on the surface rather than being soaked in. Even walls painted with ‘builder grade’ paint should really be primed before painting with good paint. From many years of experience, I’d also advise you to use good paint (I like Sherwin Williams). It’s more expensive up front, but you’ll appreciate how smoothly it goes on, and you may require fewer coats.

Since you are just painting over some small patches, you should be OK just using the same paint that you already have on the wall. Now, if the wall color is very dark, you may need to use several coats of paint to match the existing color. Be sure to let each coat dry completely before painting the next coat. If those spots on the wall receive both natural and artificial light, be sure to view the painted patches under both lighting conditions when you are color matching.

Always use a primer when painting larger areas.