In response to your questions:
- I either use the Demonstration / Manual Recording default for Capture a Screenshot (typically set to Print Screen, though you can change it), or I just make an extra mouse-click while recording and clean it up if I end up needing it on the back-end.
- When I'm trying to mask sensitive data, I rely on the "Merge into Background" function more. If just masking with images over the background you'll probably want to:
- Not use slide transitions.
- Use the masks with their properties set to "No Transition" and shown for the full duration of the slide.
Cheers!