As odd as it sounds, when I trimmed mine I didn't even look at the swash. Level? Compared to what? I can't tell. Heck, I 'm still a novice, but I still think pretty well, so I came up with my own way to do it.
I started by getting the 4 in 1 absolutely spot on. There is no rotation in my heli, so all I was dealing with was fore / aft / lateral movement. And that's where the trim slider positions told me what to do.

In my case it always lifted and went right. I could almost correct it with the trim.
With the linkage in the second hole ( the way they come from the factory) 3 turns of the linkage equals the movement of the trim from center to fully one direction (ie; moving the trim from fully left to mid range = 3 turns of the linkage). So I turned the linkage 3 full turns and flew again. I needed one more turn and it was just right. Then I did the same with the other link. When I was done, the heli will hover with no rotation and no drift with the sliders centered. It's just a few adjustments. Takes about 15 minutes on a bad day. OK, so there is no drift indoors until the heli makes its own wind and that wind makes it drift.

Soloboss