Watch the Milan Pavan: Strain 5 online guitar lesson by Andrew Leonard from Beginner Method for Classical Guitar
Strain 5 of Milán's "Pavan 1" introduces a new right hand technique: scale playing using P & I. In earlier eras of music (the Renaissance and Baroque) before the guitar was created, scale passages were traditionally played on vihuelas and lutes using P & I. The sound is better suited for instruments of the Renaissance and Baroque since it's a much lighter sound than a rest stroke. Many concert guitarists of today still play some scale passages with using P & I. You definitely can play these scales with I & M rest strokes or free strokes if you choose.
P & I scales are quite easy to learn. If you want a little practice before applying them to the scale passages in Strain 5, you can use the first right hand alternation exercise or play the major scales, both from Section 1. As you play P & I scales use the contact points on both and keep the remaining fingers curled so the hand is not tense.
After the two scale passages, the second half of this strain is quite similar to the end of Strain 4.