Doing holiday lights and building power supply and controller enclosures out of off-the shelf ammo boxes and waterproof junction boxes means you have to drill a lot of holes in plastic.
Don’t use regular twist bits for this- you will get uneven holes with really bad burrs. Use a step bit instead! It makes a really big difference, and you can get them fairly cheap at Harbor Freight or online.
If you are using specific cable glands/fittings- find a bit with steps that match the openings you will need. Narrower ones tend to work better as they give you a bit more detail between steps.