Using a paint gun is easy. Clear out or cover other stuff in the room so that they don’t get wasted. Blend the drywall compound with water according to the instruction. Make sure you blend them properly, otherwise the nozzle will be clogged.
If you don’t know how to use a drywall texture sprayer, practice with an old piece of plywood beforehand and then start spraying. Stand 3-4 feet away from the wall and start with the top portion. Put the mixture into the hopper and press the nozzle to start applying paint. Spray side by side and make sure no spot remains untouched. If you spray excess paint, scrap it level with a knife.
And yes, take proper safety measures. Use a dust mask, safety goggle, cap, and gloves. Wear old clothes that you can get rid of later.