Ok I'm curious as to what's your method then, as having a simple visual aid to get you set up seems the easiest and quickest to me. Whether you trigger or not starting from the same point each time aids consistency.
The reason I mentioned trigger movements is because it's humanly impossible to repeat the exact same trigger movement every single time. Sometimes it will vary by half an inch, sometimes by a couple of inches, sometimes it'll be even more than that because of adrenaline, fatigue, premeditation etc.
The longer you play cricket, the more your trigger movement changes or becomes more exaggerated and yet most people still use the same guard that they've been scratching out for years.
Now we're all agreed that one of, if not the, main aims when taking guard is to make sure you know where your off-stump is right? Insisting on machine-like precision when marking your guard in the ground and then tossing it all out of the window with a trigger movement that is impossible to repeat with that same level of precision is just a waste of time.
Even more so when the umpire at the other end is going "No, closer to you, a bit more, a bit closer again, no that's too far move it away now...no that's where you started, oh sod it who cares yeah that's middle and leg" and let's not forget that unless you are opening the batting in the first innings of the game by the time you get to the crease it's such a mess that there is no way you can scratch out a decent guard anyway.
So to sum up:
1) When you ask the umpire for your guard you're going to get a slightly different answer each time.
2) Once the umpire goes "Yep, you've got it" and you move your bat away and replace it with your foot so you can carve a trench with your spikes you've introduced another margin for error into the proceedings.
3) If you've got a trigger movement then your feet are in slightly different spots when every single ball is bowled even if you start from exactly the same spot every time, which you aren't.
I take guard on leg stump (My bat is on the ground in my stance so this gets my eyes in line with off-stump) and all I do is look down and use my eyes to put my bat and toes in the right spot. That's more than accurate enough for any of us.
We can pick the difference between a leg-break and a googly in a fraction of a second from 22 yards away and get in line with a ball coming down at 70+ mph but your eyes aren't good enough to judge if you're in line with a stump which is an arms length away?