I have found that learning the techniques found all the different codex(s) sets a good base for you to learn upon. Eventually you develop your own technique or method that works for you.
I always buy more models than I have painted. I have trouble buying a box at a time and focusing on them from start to finish. I prefer to build and prime. Then when it comes to painting I will take a big group of units, mix paint to my liking, and do a base on multiple units and leave them be. Often it's sloppy but I know I will clean it up when I feel like adding the detail - and highlighting/ fancy base is always the very last thing on my mind save for special characters.
I like to go home, pour some whiskey, and have a surplus of units to pick from. I will grab one and work on that one for the night until it is done (minus highlighting and basework). There is just days you don't want to work on a small unit and days where you don't feel like painting pewter or bothering with a vehicle which is time consuming.
But at the end of it all - you have an army built, choices to choose from when you play, all are primed and most have base coat of your chapter's colors.