Since you don't do much level 5 you will need tools for the job. The basics are paint rollers and wiping blades. I don't want to tell you to buy an expencive spray rig or graco sprayer since you don't have experience using one I'm guessing.
So buy paint rollers, good sticks to use the rollers with and make sure it's all heavy duty really good quality stuff. Drywall mud is heavy unlike paint so get the best most professional heavy stuff so it all doesn't fall apart.
Save a lot of time by buying a wiping blade or feathering blade they have so many names.
You need to buy lights, good lights not cheap halogen lights haha. What brand do you use for your impact hand drills? See if the brand you use also makes lighting and buy some. That way you can take advantage of the batteries you already own.
You will need umm maybe 220 or 180 grit for your poles or electric sander.
My advice is to do a really nice level 4 then roll a really thin layer of joint compound on the walls and wipe it with smoothing blades.
Don't let it sit for too long aka don't let it dry for to many days or your mud might get too hard and you'll be wanting to slap yourself for letting it harden too much.
Any patches you do after sanding level 5 will be fairly obvious once it's painted so try to have a job well done before you roll and sand. If you need to touch do it after you glazed the job but before you sand. Just go around with lights looking for imperfections and touch them up. If you do it after sanding it'll look bad once painted.
Guess that's it oh right you might need fans to help the site dry, large industrial dehumidifiers also help speed up drying times. For now just buy metal fans, a large dehumidifier seems like a bit much for now haha, and set them up in bathrooms and closets other places without moving air.