In PS you can Change the hardness setting of the brushes. So start there and don’t use the airbrush.
Try waiting awhile before you get into "blending". Just concentrate on shapes and value. You can add color and edge control to your list of things to master after you are done with those two. No need to get caught up in too many things at once. Divide and conquer. Be methodical about your approach to learning. As with any technique, repetition and practice are your best allies.
Read a little about how John Singer Sergeant approached his technique and study. It will help you realize how much work any great artist puts in to his craft. Even if you are born with heaps of natural talent, it is the determination and training that will make you successful.
My 2 cents.
I hope that helps.
***have a nice day***