See the chart I'm posting here for some possible chord voicings you might use for "O nó". Sorry I don't have time to make a video! This one is a polca, and I'm sure you can find videos online that demo a basic polca "levada" for cavaquinho, the most basic version of which is played as "1 & uh 2 &", all in downstokes.

In addition to the accompaniment our teachers have provided, I'll recommend two other reference recordings, one with Luciana Rabelo on cavaquinho:

The other with (I think) Jonas Pereira da Silva:

To my ear, on both these recordings the cavaquinho pushes the last 16th note of beat 1, which -- without quite making it a maxixe -- lends it a little swing.

Here's the chart I prepared:

Happy polca!