I' ve used masking tape for some batches, and on others I' ve made a pencil mark on the shaft and caaaaarrrrefully dipped to that exact mark each time.

With the masking tape, it can leave quite a " ledge" between raw shaft and dip area after you dip 2-3 times and then peel off the tape. But you do get full bold color right to the line, whereas if you dip to the mark you may have a bit of " thinness" in the color right by the line because the paint is running away from that line on each dip. Try both ways and see what you prefer.

In fact, you can see example of both ways in my pictures. In the second picture, look at the lower shaft in the crested silver area where the white dip ends, you can see a slight ledge under the silver paint. That was done with masking tape.

In the bottom picture, look at the slight amount of thinness in the yellow color where it meets the raw shaft area. You can see where that color is not quite as vibrant as it is further towards the rear of the shaft. That is the dip-to-mark method.

both ways will work fine-