I'll lay out some things I've learned, particularly in the last year or so, that are effective at these sorts of events. Be mindful that much of this is situational, so adapt accordingly.
For starters, bring a table of some sort as well as something to provide other protesters. Water, coffee, snacks, etc. This will provide an opening for engagement. Also on the table, printed material. I suggest bringing material from your org despite your reluctance stated elsewhere. You never know who might be in attendance and you might find attendees who are more open minded than you think, especially considering current conditions. I helped set up and work with a local org that is anti-capitalist/anti-imperialist and works to build community and solidarity in the immediate area. Despite what others have said, not everyone is ready to dive in head first to socialist/communist ideas. This org acts as an entry point for those people as well as providing mutual aid and community defense programs. It's also a sort of pipeline into more theory heavy groups once they reach that level. I bring printed material from this org as well.
Your ice breakers stated elsewhere are good, but depending on the situation, might want to reeled back just a bit. I've had great success with "Trump is the symptom, capitalism is the disease" on signs. For MLK and Einstein, maybe print out a relevant quote and leave it at that. These libs often need to be handheld and this is a good way to ease them into things. While somewhat bothersome in my opinion, the terms Epstein class, pedo class, and billionaire class are effective for strengthening the idea of class consciousness. In reality it's all referencing the capitalist class, but you can get into that later.
I brought up whether you are known because this determines how deep into the theory you can effectively go without scaring off folks. I've been going around to local lib protests for the last year and have made a name for myself amongst many. They know what I'm about to some degree, and have become comrades in other endeavors. Many are ready and willing to help out with mass orgs, which opens the door to further radicalization like the other org I mentioned above.
If you have the willingness and ability, find a chant book and lead them in chants. If you have a megaphone, that's even better. There's hardly any leadership and organization at these things, in my experience. Fill that role.
I understand your frustration with the marches as you also stated. I'll keep my own opinions of PSL to myself, but the marches do serve a purpose as well. Aside from being a good way to raise awareness and educate with counter-propaganda, they are good places to network and meet like-minded people which will be crucial in the days ahead. I've met many at these and other events that have joined me in labor organizing and mass org work that have proven invaluable.
Good luck out there comrade.


comrades talk at these lib-attended events we definitely talk socialism, but you don't just shout the word. Talk about the billionaire class and that their interests - especially this imperialist war - can never be resolved at ours.