1)
This is a quality any good leader needs to understand, if you examine any person who has moved you to act in a certain way they had to understand what you specifically want and tailor their message to your demographic in order to effectively sway you to their side.
In mafia, its not different.
Everyone has a win condition, and its easy to say "Both our goals are to eliminate scum, join me on this wagon because it will lead to you furthering your win condition" in practice, that is rarely enough to actually push people to act with you.
2)
This means you need to understand not just what a person wants in terms of who they want to lynch, but WHY they want that. What does the person your trying to convince think is the determining factors whether a person isn't aligned with you? Tailor your message to hit those points. Maybe someone reads players by VCA, somehow try to frame your reasoning using that to express why they should be joining you to lynch who you believe is not aligned with you.
People tend to agree with people who behave as they would. This could mean posting style, word choice or just voting pattern. The key here is you can use those to try to target a person and talk as they would talk, and behave as they would, they will be far more receptive to your attempts at persuasion.
This is an obvious one, but people will gravitate to players who exude confidence, the key here I believe is that you should never FAKE confidence. That will cause you more problems because people will pick up on you faking it when you start showing cracks in your facade. You should be honest about what you are confident on and what you aren't, and yes that sometimes means people will not be swayed by your arguments, but people will believe you more when you say you are confident on something if you have a history of being upfront with people on what you are and aren't sure of. Lying about your confidence will only hurt you in the long term, it will lead to blind arrogance and people thinking you are full of it (which honestly you will be if you have been faking it).
Do not outright dismiss anyones argument even if you 100% disagree with them on every level. Talk to them, say why you think they are right but also affirm them of something that you do agree with. Perhaps you like the way they came to conclusion but you don't agree at all with that conclusion. Or you think they are right but they missed some steps logically, a charismatic individual will give credit to a person when they do something right and point out in a nice way where they may have messed up.
You will not win everyone to your side. Don't attempt it. If one player hates VCA and you push an argument using VCA you may alienate another player while you tried to persuade another. You should try to keep your message in a way that convinces the most people you think you will need without trying to convince everyone. This can be hard, but some people will just disagree with you no matter what. Even if you frame it in the way that is convincing to them if you made another argument they don't value they may see both arguments as invalid.
You think you made an excellent case why X is scum? Great! But it will get lost in the noise. You have to repeat the message constantly, so it sticks in peoples minds. I would recommend never Copy and Pasting the same post because people will think you are just spamming and being a nuisance, always try to find a way to rephrase your message but keeping the heart of it intact. Maybe the way you said your case the first time just didn't have the right wording and the second time will broaden your reach to players who didn't agree with the way you said it the first time.