There are different ways to paint. Contrast paints are supposed to make things quicker and easier(though I haven't tried them).
I rely upon batch painting for efficiency. One day prime everything at the same time. Another day paint with one color on multiple minis. For example paint all of the skeletons and stone buildings dark brown if you haven't already primed them that color, then set the stone aside for grays mixed with browns to be added to them later. in successive days dry brush all of the skeletons with lighter and lighter colors (eg. brown, beige, etc.), then avoid putting lighter colors on the wood elements of weapons and such, but continue to dry brush the bones with bone, off white, etc. And maybe put a brown or black wash on them at some point in that process before the final dry-brushings. Go over the finer details of weapons and stuff later with other colors. I like to put a burnt sienna wash over metals for a bit of rust. But the point is to only have one color of paint out at a time and apply that color to as many mini's as possible which need that color. You might only use one color in a day, but eventually you'll have a lot of painted mini's.
As an example, I could paint the red spider, the goblin coat, and some other spider eyes at the same time, and I think the white spider may have been painted at the same time as skeletons:
And I painted the brown spiders at the same time as painting some wood, but just took the wood a little further with lighter colors.:
Paint brushes can require maintenance time and are expensive, so for some circumstances it's easier to paint with toothpicks and needles(or pins with a ball on the end). A wet palette is the ideal palette if you're using dropper bottles of paint. Make a simple wet palette with wet paper towel in a tray or in peanut butter lid with parchment paper on top, and paint put on top of that. But to save the time of dealing with palettes, sometimes I'll just dip the needle or brush directly into the open paint lid which I remove from the bottle. I'll put the lid back on and shake it when the lid is empty to bring more paint to the lid. After applying the paint to the mini, stab the needle in cardboard to remove the excess paint from the tip before dipping in paint again for the next application, as it dries quickly on a needle and you don't want to paint with a needle caked with dry paint. Toothpicks carry a bit more paint than needles and sometimes work as well as brushes for certain small things like belts. Wood fibers of tooth picks can retain more moisture than needles so they need less stabbing into cardboard and re-dipping, and it might help if they are damp tooth picks.
Light, magnification, and a space to work will be necessary; ideally a space you can leave messy so that you won't have to spend time organizing it between paint sessions. Imagine a ready station: You'd only need to open one paint and focus on applying one color to mini's for as much or as little time you have available.