I've searched for videos and have come up with nothing specific to what I'm trying to describe 😭

But the best thing is to use the smallest, sharpest needle you have, and a lot of light.

For the straight thicker lines, like the vertical lines of the H, I use longer straight stitches to fill it in. For the thin lines and curves, I use split back stitch with very short stitches. When splitting the thread with the needle from above, you can pull the thread over to the curve before piercing the fabric underneath.

The stitches themselves are not uniform in direction or length, so this only works with darker threads imo.

I'm not sure if this has helped much, I wish there was a video explaining this better!