a) its about quality, not quantity, best have 1 true friend and a hundred acquaintances.
b) anyone can be redpilled, but the conditions will vary for every one. the best way is to get a firm grasp of their belief system, and work from there.
1st you identify the strong and weak points, have him talk about himself a lot, ask questions, ask hypothetical scenarios that challenges his beliefs, and try to find the limits,
never give your input unless asked.
this is important, if he asks then its a sign he is willing to listen, could also be a test so only show part of your hand, or give your actual position but make it sound uncommited, that you could always be convinced otherwise. This is where they often go on the offense and try to convince you, and this is where ya offer proper rebuttal that shatter his argument. It also wont come off as preachy or pushy since he started the debate.
once someone share or understand your position on several weak subjects, then ya can start to groom. use actual events, especially news that are related to some of his weaker stances. Call out loud what the TVnewsman as saying bullshit, or the newspaper idiots without a brain, but dont say more than that, people are genuinely curious, and he WILL then ask why you are saying that, you can then start redpilling propper, small stuff at first.
It is important that the target feel he is the one changing his mind on his own rather than you shoving the redpill
that is why he need to be the one challenging his own perception of stuff, he will only do so if he value your friendship and/or input and does not feel threatened by your position, this is why you rely on first forcing them to think by probing them with scenarios that test their beliefs, to the point where they start asking for a different point of view (yours), once he opened the door ya can start baiting him to ask your more questions by doing incomplete commentary on stuffs.
once you molded him enough to weaken all of his weaker stances and beliefs, ya can finally attack core ones, here is where the prep come into play, you start asking direct questions that challenge their stance, for example "why is nationalism bad?". If ya already prepped him by having him ponder about related stuff like:
-why israel or saudi arabia refuse refugee but we must accept even though Arabia is more compatible and more wealthy and more able to accommodate them,
- why can someone be proud to be black, or jew, or latino, but being proud to be white is a sin?
- or how European countries lost their ability to decide for themselves because the EU force them to follow their policies, regardless of the will of the people.
then a real dialog can occur and when one of his core belief is laid low, ya can hop in, and say why YOU think nationalism is not a bad thing.
All of this is of course for friend and people ya care about, people ya don;t care about can pushed against the wall with cold hard facts and be forced to swallow it, or go in denial and retreat to their safespace, and everytime they try to come out they need to be stonewalled with more redpills until he either have an epiphany or have a mental breakdown. The mental breakdown is more frequent, but also as useful because when they do so, other people following him get in turn distraught by the reaction and end up awakened by proxy or fearful of similar effect on themselves.