Got my 1st ExRaid Invite this morning....How is catching M2 like? Easy or Hard?

The story you told is actually non-sense. Unless you throw away balls, there is nearly no chance that Mewtwo will run.

I caught 3 out of 3 Mewtwos already and hoping to catch my forth tomorrow.

Tips is that be calm, take your time. You will probably be nervous in throwing the balls. There has been some changes in Mewtwo distance, so I'm not really sure which pokemon is comparable.

Another fast tip is that don't throw the ball too early, since there will be some time interval before the circle appear after Mewtwo moves his hand. You will kind of get the timing soon as you will face him in the catch screen. So, again be patient!

If you're already comfortable with your throwing technique, the best advice I can offer is this: move away from the crowd (you don't have to remain near the gym once the catch sequence has started), sit/stand someplace quiet if possible, get comfortable, take a few deep breaths, and take your time throwing. Use the trick to set the circle where you want it, and wait for the attack animation to wind up your throw to avoid your premier balls getting batted away. Also, it's better to hit great throws every time than to aim for excellent throws and miss the circle, so if you're finding that excellents are hard to hit, resize the circle and go for greats. Since Mewtwo is basically the crown jewel of Go due to the exclusivity of EX passes, the catch sequence can be nerve-wracking, so patience, a steady hand, and some well-timed curve balls are key.

Good luck with your EX raid. Hope you catch it!!!

The probability of any person who can throw a great curveball missing is very low but it does happen. Stay calm don't be a pinapp hero wait for your moment. There are heaps of videos of the attack animation on the web watch them.

I've seen it happen where Mew2 ran away, even with 10+ balls. It's still RNG. However, the vast majority of people do catch it in the raids I've observed.

The set-circle-wait-for-attack trick seems to work best for a lot of people, especially when the legendary is very jumpy. Throwing consistent greats is better than missed excellents.

60% of the time prodogiesnation technique works everytime

First of all, Mewtwo has way higher catch rate than Legendaries.

An Excellent curve throw with Golden Razz gives you a 40.51% chance of catching it (if you have gold in Psychic, which I think most have). Even a bad throw gives you just short of 25%, which makes it possible to catch Mewtwo even with a terrible throw.

But, this does of course not mean you can be sure of catching it. Even if you get like 14 balls and has perfect throws all the time, Mewtwo might still be a jerk and run away.

When I did my first EX Raid (will do my 2nd on the same day as you) I didn't hear about anyone not catching it and on the first EX raid in my area (which I missed out on) I've been told that almost everyone caught it. 2-3 missed it that time and they were like 40-50 people there (maybe more, because they did like 4 groups). In the most recent raid two people failed to catch it (one of which a little boy who, naturally, began to cry - I hope that doesn't happen during my raid, because it'll break my heart). Not sure how many were there, but as you can tell, the percentage of people getting it is really, really high.

My suggestion is to just try an relax and take your time.

Also, look on YouTube for videos about catching it, but beware of when the videos were uploaded since the distance changed recently.
Here's one video I found: https://www.youtube.com/watch?v=UU0v7De7dNA
Hope it helps.

And good luck with the EX Raid. I hope you catch Mewtwo.