In the beginning, we match up the modes with the corresponding harmony. This means when the Dm [the ii chord in C] is sounding, we are thinking & playing Dorian [the 2nd mode in C]. Yet, we don’t have to think D Dorian because if you are playing the Dm chord & soloing in C Major, D Dorian happens automatically.
If we know that all of the chords in a progression are in the same key [such as C Major], we can make one scale choice.
Note: a chord symbol is also a scale symbol. Just as the chord can be realized in any way which we deem appropriate, we can also interpret the symbol into any scale which sounds good to us.
The modal formula is under the tone names. This is comparing the scale components to their corresponding Major key [i.e. we compare D Dorian to D Ionian]. We can see that the number of sharps or flats in the key are the tones in the formula that are sharped/flatted.
We can play the chord changes as scales, octave to octave, root to root. There’s some blank tab there. Print the above graphic. Write chords [which you order] above the tab, and play the corresponding modes as written, then follow your progression, just improvising, while still making conscious choices. Write down any melody you may want to remember.