The only difference between layer by layer and f2l is there is less steps. Your still putting the same 2 pieces in the corner, just hitting them together first.
How long does it take to get faster? Well it's kinda a little bit at a time. I managed to drop 10 seconds in a few months then stopped practicing and now I'm back where I was...
Honestly when I was where you are the greatest revelation was learning sledgehammer. It has so many uses, more than sexy move in my opinion.