We used 2 lb balls just about every day. For a starting program, you should work your way up from maybe 1 set of 5 reps to 1 set of 10 reps as you get comfortable with it and up to 5-7 different exercises. I probably shouldn't post the exact exercises we use (Wolforth would probably prefer to sell his program rather than me give it out for free), but basically you are throwing it against a brick wall (or something hard). Try to look through some of Kyleb's exercises and make sure you are using exercises where you throw frontward and ones where you throw backward. On the backward throws, make sure you're keeping your elbow stable at shoulder height and flick your forearm backward at a 90 degree angle.
In addition to the aforementioned prehab stuff. we also use weighted balls for velocity increase. I'd recommend 2-3 days a week for these exercises. For a starting program, you can work your way up from 1 set of 2-3 reps per ball to 1 set of 4 reps per ball. We use the whole gamut of weighted balls but start with the heavier and work your way down to the lighter. For the different exercises, you could progress from an exercises with static feet; a simple step and throw; a step behind throw; and a crowhop.
I can try to answer more questions if you have any. I'd highly recommend a program. My arm felt weak and tired when I started it, but eventually my arm felt better than it ever had. Now that I am off the program, I can really see that it made a difference. Good luck.