Estimate time for pronunciation drills.
Pronunciation is motor learning, so it responds to high repetition counts spread across many short sessions rather than long blocks. Twenty repetitions of twelve sounds at four seconds each is a sixteen-minute session, and reaching automaticity typically takes on the order of fifteen such sessions per sound set. The total repetition count is the honest measure of the work involved.
Session length
Session minutes = sounds x repetitions per sound x seconds per repetition / 60
Total workload
Total hours = session minutes x sessions to automaticity / 60
Sounds absent from your first language, or that fall inside a single native category, are hardest because perception has to change before production can. Minimal-pair listening drills usually have to come first.
Very — self-perception of your own accent is unreliable. Comparing a recording against a model reveals differences you cannot hear while speaking.