When starting, select your mode and difficulty, then wait.

Once all the pieces drop in the background, press 'continue' and begin playing, your time will start here.

Fiddle around quickly and see if you can spot any potential areas to make a star. If you take longer than 30 seconds, I recommend restarting, unless you feel like going on.

This is a tedious, but safe, way of guaranteeing a low time for these two categories. However, expect a good handful of resets.

You can then go on to apply it to the other modes if you want a low time there.