Well I learnt the 'proper touch-typing method' because well...I'm not going to lie...I thought my first mech 'board was a waste of money and did not feel different - quite the opposite now. In other words it was justification for me keeping an expensive keyboard without returning it. Plus I always wanted to 'type properly' because I thought I couldn't.
Previously, I had typed for many years but I did not naturally adopt my own efficient touch typing technique. Sure I could "touch type" although it was a bit inconsistent (e.g. typing T-H-A-T = MID-IND-PIN-MID)and admittedly I would have to still glance down when I 'lost my place.' So depending on your definition, I actually couldn't. Anyway, now that I think of it, if I naturally found my own 'home row' then I probably wouldn't have to glance down to return to whatever I returned to at the time, although I cannot remember what now.
I would describe Wrona's technique as an incredible visualization anticipatory skill, which is quite amazing in my opinion in order to do that. I obviously could not do that, so that's why I put time aside to learn the 'proper touch-typing method' which I always wanted to do, but never really bothered putting in the time and effort but forced myself to do when I got my first mech in order to justify it's cost. And it sure is paying back dividends.
And now, to answer the Thread Starter's questions:
1) "backspace" key using the right pinky?
I type colemak. Backspace is on the former Capslock key. I use my left pinky.
2) use both "shift" key to capitalize?
Yes, I try to use the opposites. Admittedly, when doing typing tests and depending on the position of the previous key, sometimes I use the closest one e.g. left-shift for T.
3) use both thumbs to press the space bar?
I swapped spacing only left thumb for only right thumb because my left thumb was hurting.
4) press the numbers and symbol keys with the correct finger?
Yes, always. Even the stupid ones such as 6 and 3 with the middle.
5) any other keys pressed with the wrong finger?
No, I am pure - or rather stupid