There are several techniques for producing fine white, or lighter, lines on a dark background (typically when drawing hair).
You are correct that erasing the line is one of the techniques. I use a Tombow Mono Ultra-fine 2.5mm round eraser. This should be kept trimmed with a craft knife to get a clean sharp edge. You can also, I believe, trim a block eraser to a fine edge and use that, but I have never done this.
I have also used a kneadable eraser pinched into a fine edge. I keep a selection of balls of kneadable eraser, some are quite soft, being new, and others are stiffer, being older and well-used. These stiffer ones hold a fine edge better. This method is more useful for more general highlights, rather than individual hairs.
Another way of producing a really fine white line is to indent the paper with a stylus (I have variously used a wooden point, knitting needle and a ‘dead’ ball-point pen but now use Royal Langnickel embossing tools). These produce an indentation in the paper that when you shade over it, with the side of a pencil point, the graphite does not get into the indentation. If it does fill with some dust, you can lift it out with the fine edge of a kneadable eraser. You can also use a finely pointed hard pencil. It will leave a pale line, which has the advantage that you can see what you have drawn, but it will never appear white in the drawing! Whatever you do of course, there is no way to erase a mistake or fill in the indentation! You could, before you start, lightly sketch where you want the indentations.