Is the wall dash method easy to do? Because I've done it on first try and then all of a sudden I can't do it anymore. Is there specific timing to perform it or is it just dumb luck?

The timing isnt as important as where you line up on the door, it's pretty precise. I'd recommend looking at Emilio's 2:34 run, you can see all of them that are used and where he lines up. It tends to be the same for each version of the same door type (all remnant doors work similarly, for example), but different door types have different spots. There's still a bit of randomness when you line up properly from what we can tell, but it can be virtually impossible to get through if you aren't standing in the right place

Thank you for the advice. Hopefully I will get them on first try during my speed run.

Update: Still can't do it even with the advice. Either Bioware did a secret patch or I just can't do it anymore. If there is a tutorial on how to properly do it. I really appreciate it. >:(

Update #2: Manage to do it (Thank god) turns out there is a timing after performing the melee slam during its recover animation to perfect the wall dash and you have to perform it on the line of the door just like you said Letter. So everything is A-OK. :)