Spray some WD40 on a rag, and wipe down the end caps and metal arms of your rollers before dipping it in paint. After the job, the paint will clean off easily. Literally wipe off. Keeps roller frames brand new looking. Also spray the inside cage.
When finished with a 5, use a screwdriver to pry out the rubber seal around the inside of the lid. This works great to hold a piece of plastic over your current paint 5 over night (or during lunch, or over a weekend) while on a job. You can throw a wet rag over the 5, then cut a piece of plastic to cover the whole top, and the rubber seal works like the perfect sized rubber band. Keeps paint fresh for a couple days like this.
When using premix mud, never mix or pull mud out of the 5 it comes in. Scoop out a portion at a time into another clean 5, add a splash of water and dish detergent, and mix it with a drill/paddle. If you mix it in the original 5, or pour off that water, it will dry around the edges, and get chunky. Also always wipe off the inside of the lid when you crack it open to keep the residue from drying out and falling in the mud.
Also sometimes I put a shot of food coloring into the mud I'm using so I can see the repairs on the wall/ceiling. I hate when I'm painting and I find an un-sanded patch that I couldn't see or just plain missed while sanding. Make sure not to put too much coloring in there that it makes it tough for the paint to cover.
When I buy new metal screens for a set-up, I hit them with 2-3 coats high gloss oil from a rattlecan. After the job, throw the screen in a 5 of water, the paint peels off like a skin. Ready for the next job.