Hi Steve! Well, you did a great thing changing up the pick as the jazz picks are more difficult to use in a song like this! As for dropping the picks - this is more common than you would think, and from time to time I struggle with it a bit.

The best advice I can give is to be intentional during your practice time. For example, in a song like Kiss, I would work on making sure my chord fingerings and changes are comfortable and correct. Next I would tackle the specific strumming, slowly of course, so that I am getting the strum pattern down properly.

Once you've practiced both of those, they can be a bit more on "auto pilot" if that makes any sense, then you can practice while focusing your attention to holding on to the pick. In my experience, it's a combination of your strumming arm and wrist staying as relaxed as possible, but at the same time gripping the pick with enough pressure to keep it locked between your fingers. It's not as easy as it sounds, but the idea is that with repetitive practice, you'll be able to do this without thinking about it.

Hope this helps, please let me know how it goes!

Mike