I REALLY REALLY want to do this…

BUT…HOW MUCH TIME TO DO THIS__?

its a page from black cover manga.

but…cmon..those are so much details…

the question is…

they used some software to do this? 3d? blender? after effects with some plug ins?

plz help me improve thx!

PD: I just uploaded new page!

Mangaka got a whole paid team working on this stuff, but also that level of detail is why the author of Berserk died (they are all super over-worked to get a manga out in time) so the answer to that is “have no life outside comic”. Don't work yourself to death trying to micromanage details, especially if they'll be crunched in reformatting or glossed over in pacing. Detail sometimes gets to a point where one is showing off instead of focusing on the real meat, that's the story and characters. Also pace action that requires huge amounts of detail too, something like this should be for only once in a while because if it happens all the time it loses impact. If you're doing that every other page, people will start to take it for granted as well. I know from experience once you commit to overdoing it you'll find it hard to “simplify” when you need it. Plenty of comics get by on keeping a certain level of detail-simplicity balanced so pages where detail is suddenly maximum high just hit harder.

Some modern mangaka do use 3d rotoscope technique (Way of the House Husband does this, there are 3D to 2D art conversions) but this looks like someone did that all by hand, as there's a lot of variation in the stones/rubble flying. Some things you just can't trust the robots to do for you!

But you can find rubble/flying rock brushes easily for Clip Studio if it's what you work with, even for free. Get ones with a lot of variation options and mix them. I see some excellent comics out there use premade assets like image brushes, only the folks that know how the sausage is made will notice or care. Haunt the stock section on Deviant Art you'll find some excellent stuff on offer (some of it you might have to pay for or include credit though just read their terms before downloading).

Though my personal preference is to wander off what I'm doing and make 30 different rocks for a brush I'll use once. But it's good to have for if I need to use it twice. I just have a fiercely independent streak and want all my brushes to be made by me even if includes making a brush entirely like the one I got default with the program!

Everything Amelius said.
The art of comics is also party about suggesting a lot rather than drawing every minute detail too and that's something to be learned. If you look at this piece really closely, though the artist has spent a lot of time on this, they've also implied a lot more than is there.
Look at the brick and you'll see not every brick is a complete brick and few are carefully rendered. behind them are black areas with brick shaped edges. The complete walls have patches of brick drawn in here and there - your brain fills in the rest. It's an explosion, so fast penwork adds to the effect too. Most of the hatching doesn't describe the surface it's covering and that would be distracting. Less is more, especially if you're going for something this busy.

A lot of comics are digital these days and make use of pre-made assets. I've seen at least the speed lines, the Japanese sound effects, and rock / debris brushes that look pretty similar before while browsing through Clip Studio Assets. In my opinion, the best way to learn how to do something like this for yourself is to try and do it yourself.