As mentioned, you don't really have to study for pt3 student boards (just take it right after pt2... same info).
The studying, for any of these exams, began years prior. You won't suddenly learn all of the anatomy or the micro that you failed to learn back in basic sciences years. The actual time leading up to the exams is just to learn the exam format and to brush up on what you know, review high-yield and oddball stuff (classifications, bone tumors, abx and bugs, etc).
You got info for pt1 student boards through years 1 and 2 of pod school.
You get info for pt2 and pt3 of student boards from 3rd year pod school and clerkships.
You study for ABFAS BQ during later school and residency, etc.
The bottom line is just to apply yourself in the classes, pick places (school, residency) that help you prep, and just do reinforce and high-yield leading up to the tests. Part 3 is basically the same as part 2 (minimal competency, easy for anyone who was half awake in pod school).
Of course someone who barely passes the classes in pod school might fail APMLE.
Likewise, someone who doesn't read much and goes to a residency that does little/no academics or board prep is at high risk to fail ABFAS.