Perhaps a topical outline of the 29 December letter from the Universal House of Justice might help in its study. If so, here is one (Topical Outline of 29DEC2015 Letter from UHJ)

It is interesting to note that the headings of the letter seem to define or succinctly characterise the essence of the milestones.

1st Milestone: The emergence of a programme of growth

2nd Milestone: Strengthening the pattern of action (Intensive Programme of Growth)

3rd Milestone: Embracing large numbers and managing complexity

If you wish to download a chronological (by paragraphs) outline/summary, please click this link.

If you wish to download a summary/excerpts of past messages regarding achieving the 2nd milestone, please click this link.

You can also download the UHJ Letter dated 29 Dec 2015 with numbered paragraphs.