Frozen Run,
You are learning, and that's an important goal in itself!
Regarding the engrailing, are you struggling with the spacing, or with the cutting?
For the spacing, I usually just look at it from the end and put 2 pencil marks directly opposite each other. Rotate it a few times to check them, and adjust as necessary. Then turn the horn and put marks half way between those first marks. Again adjusting as necessary. Then add marks between those marks, and so forth, bisecting each time until the marks are evenly spaced and of the spacing I want.
It's also possible to wrap a piece of tape around it, mark the diameter on the tape, then take the tape off and stick it to something flat and slick, such as a counter top. Then measure off your spacing on the tape. When done, then pull the tape off the counter tip and put it back on the horn and transfer the marks.
You may want to add a line behind the engrailing, as well, to help you establish how deep you want each cut to go. This will mostly be determined by the shape of the gouge in relation to the spacing, but it can still be helpful to have a line to look at.
As for cutting, I do it with a gouge.
With a gouge, I take small bites, again and again, until I have finally cut it as deep as I want. I find it best to cut between the marks, leaving the marks until the very end. I go around and around the horn with tiny bites, working on consistency, taking small bites until I have cut out the area between the marks, then I stop. Maybe some guys just do it with big bites of the gouge, but I just find it easier to get good cuts and consistent spacing if I do it the way I explained. You have to adjust the angle of the decent so that it scoops out the material, rather than just diving in deep. Imagine what you would need if you were trying to carve a wooden spoon. Each dip in the engrailing is like 1/3 of a spoon-shaped depression. If you aren't used to controlling gouges like this, then you could practice on the edge on the end of a piece of hardwood.
Hope this helps.