Are you the "know-it-all" in your raid group?

I look at this way....

Informing them once is trying to help, so by all means help when you can.
They can choose to accept your advice, ignore it, or ideally investigate your advice to get a better understanding.
If they choose to ignore it, then let them - sometimes the best way for someone to learn and gain knowledge is to do it for themselves and gain from the experience.

I get that it is a fine line, but at the end of the day it is up to the individual if they want to take your advice - and repeating yourself won't often change their mind.

That said, if they ignore you a couple of times, and then find out for themselves that you are right...then they may learn multiple things from their experience - one of those things being that your advice may be worth listening to in the future.

Basically, if they want to work it out for themselves then let them...at the same time they will also work out your advice is solid.

Apologies if this post makes me sound like a know-it-all (again) ;)

My Mewtwo raid on 11/11 brought me to the east side, I work there but rarely play/raid there...I went in and checked the moves: (seemed to be a foreign concept, we had a hard start set for 3:05 pm) Confusion/Psychic...told a loud guy to not use Gengar, I also added Lugia is a terrible idea...normal stuff. Most people were quiet and calm, duh dark/tyranitars.

I did see one of the leaders of the earlier Mewtwo raid at a Machamp Boss, he seemed to be receptive on how I could solo it with a lot of time to spare. However, right now, anybody I see raiding in my normal area is only lacking clues in the sense that they are still trying to raid several times a day.

If you want them to be at knowledgeable as possible, then point out their mistakes, who cares if they're embarrassed, it's a game.

Its best not to assume. One of these guys told me Vaporeon was near impossible to solo back in the day. I proudly [arrogantly] posted the kill screen. You never know but I agree its fair to share what is most likely to happen as long as you're sure not to he telling someone what they can't do.

I tend not to feel it necessary to correct people in public unless they are spreading misinformation as fact, which I can't abide.

Lol I can even get one down to red with my level 30 Vaporeon team.

I actually did never like people who are asking every bullshit because they want to play "perfect". If you ask everything it's like another guy is playing your account. I mean its like having the solution book to do the exam. So I don't feel that bad for them, when they are told wrong. (my opinion before playing Pokémon Go)

BUT as you said you need them to do Legendaries. And there are so many players who have absolutely no clue. That's terrible if you are in a town where you don't have that many players. Specially when it's starting to get cold and even less people are available. So you should try to take influence. Specially if they let it happen. Giving them hints like "Don't use Steelix" can help and don't destroy your image but if they decide not to listen there is nothing you can do about. Logical explanations are mostly pointless. Just try to get "the Boss" of the group on your side or be him yourself. Most people are like sheeps and they'll listen and follow

Took time but it works. We were able to do Entei with 4 and Raikou with 5 players (on regular base and not with hand picked trainers)

in short: correct the guy unless he is "the boss" and you risk landing on the black list