The way I learned my much-improved release was to concentrate ONLY on the release, and nothing else, in drills. I didn't even need a bowling alley to do it. I just stood in front of my couch, concentrated on keeping my hand behind the ball and my fingers under it, having a firm wrist, and releasing the ball into it. You can use mats or whatever you have to absorb the impact of the ball.
I work my pushaway, footwork, swing, and release at home. It costs less that way
I save my practice time on the lanes for things like hitting targets, making adjustments and playing different lines, and spare shooting. That's why it looks like I'm bowling for score when I practice, because I am trying to hit my mark and throw a strike; I'm not going to practice missing my mark by 4 boards and going Brooklyn. Of course I will throw a strike line ball at a 4-6 or 6-7-10 split because I am not bowling for score and I'm not a big proponent of "split shooting practice" because some of those things can't be perfected. I'll practice baby splits and 5-7's and 5-10's if I leave them, but that's the extent of it, especially the 5-10 because I attack that one with a quasi-backup ball from the left side.