For the minminmin flicks, usage of both fingers/thumbs will drastically reduce the speed requirement for the pattern, making it a comfortable technique usable by newer players who have not developed the speed required.
One point to keep in mind is which finger is the one that swipes higher on screen. This is personal preference. Personally I would make the "visiting" finger swipe under the "home" finger as this reduces stretching. However, some people prefer it the other way around.
For the Usa- Usa- Usa- Usamin! Pattern, the most important thing to take note are the notes in lanes 4 and 5. The second "usa-" starts on the tap note in lane 4, but it's important to think of this tap note as a flick. Slide that finger out to lane 5 and bring it back in to register the trickiest part of the pattern. An illustration of the motion is provided below.