Still didn't figure out how to do that.
yur2die4 pm me a lot of suggestions and none worked, maybe i did something wrong, so i will post his messages in this thread and maybe someone will find a way how to do this. Here is what yur2die4 suggested:
My idea is a bit different and, although it would work great for performance, it might not work the quickest when starting from nothing.
Basically, instead of relying on the 8 macros of the drum rack, this relies on macros that you would have assigned to every single instance of Simpler(or Sampler) via a preset that you make.
You make a preset group of Instrument Rack (instead of Drum Rack) with Simpler inside it. Then Assign the 8 macro knobs to any parameter you want from the Simpler. Next, test it out. Without assigning anything in MIDI Map Mode, if your MPD is set as a Control Surface, you should see a blue hand if you touch the title bar of that Instrument Rack. Then you would be able to adjust the knobs on your controller and they automatically update on the Instrument Rack.
Now, you put that Instrument Rack inside of a Drum Rack. The difference with this from the vid you saw, is that you do not assign any knobs to the Drum Rack macro. This would free up the Drum Rack macro knobs for anything else you want to control (fx? sends?). IF you do have anything from every single sample that you want to control from the Drum Rack macro, then I do suggest that you assign that. I hope I'm not confusing you

Last part. This is the annoying part. Here, you would go to Bank D of your MPD controller. This is assuming that you don't necessarily use Bank D normally. Then you turn on MIDI Map mode. Next, you assign each pad to the appropriate 'sound' by choosing the title bar of each Instrument Rack within the drum rack that we made. We leave MIDI Map mode, and test it out.
If it worked, when you tap a pad in Bank D, it should automatically jump to the Instrument Rack macro knobs. There should be a blue hand on the title bar. And you should be able to control the 8 macro knobs. Then you should also be able to jump to any other pad, which does the same. You could even switch back to Bank A and hit your pad, to preview the sample while you are tweaking it.
Now I will explain potential problems, I like giving advice, but I only want you to use it if you find any of the ideas effective for your own workflow

So you may have to change some things to work better for how you work.
1. MIDI Assignments don't get saved as a 'preset' they only get saved with the whole ableton live session. So if you open a new drum rack, those midi assignments might be lost. If however, you have one rack that you are sticking to, you are set to go.
2. I actually don't have Live in front of me to test this out, but I am not sure of the behavior of the drum rack when you turn on the Auto button. There is an Auto button on the bottom left of the Drum Rack that automatically jumps to the sample you have last triggered. If THIS changes the Blue Hand assignment, then you are better off using this. Then you wouldn't have to assign any midi at all in midi map mode!

I just woke up, but I will test this out myself today. Could be very useful.
If mpd pads don't assign.
3 things I'd double check are:
1. you have the Control Surface section set up, not the MIDI in/out stuff on the bottom.
2. your preset is the "Live" one, i forget which number preset it is, maybe 7?
3. the blue hand is on the titlebar of that rack. and when it is on there, you should be able to move the knobs and automatically the macros start moving.
I guess you'd also have to make sure that those knobs are assigned to Nothing in MIDI Map mode (blue screen). they can't be assigned to a single thing, or it interrupts.
As i said, i try everything and it's not working.
Maybe someone could share with info how you sample inside Ableton using your mpd24?