THIS IS THE QUESTION! THE question I've been asking the stars.
I have read both of those, the second one seems especially useful, as it has an abundance of information. Shame I still don't get it

. I'd very much appreciate if someone revealed their tricks.
Look at the disputed succession notifier each year and see if there is any interesting nation with no heir and a 40+ years old ruler. If there is, insure that you have very high prestige (100 should be your target) and ask for a RM.
By doing this, there are basically four possible outcomes:
1) The target nation gets an heir. If that's the case, nothing happens.
2) A noble from your house gets on the throne of the target nation.
3) A succession war for the target nation occurs between you and you strongest rival. If you win, you keep the PU.
4) You get the PU without succession war.
If the outcome 2 happened, you can claim the throne of target nation and use the claim throne CB if any of these condition is true:
A) Target nation is under a regency council.
B) Target nation has no heir.
C) Target nation has a heir with a weak claim.
Another riskier strategy is trying to get another house on your own throne. When you set your heir as a general he has an increased chance of dying. Thus, it's possible to RM only your target nation to insure that their dynasty gets on your throne when your heir dies. This strategy is riskier because it may lead to very long regencies or you may end up under a PU if you're a not powerful enough, but if a house is particularly strong in Europe, it may be easier to get this house on your throne too.