You can "pull" it without actually pulling it.
You get a thinning comb (I think it's called that anyway) it's a plastic comb with a razor blade inside it and basically what you do is flip the mane onto the opposite side of the neck, and comb through it, when you flip the mane back over you have pretty much just pulled the mane, by not actually pulling it, because the blade has cut the hairs you would have pulled out.
Some people I know prefer this method because they say pulling manes makes the horse bleed??? I personally haven't had that experience though
R.I.P ~ Bubbles - 25yo tb mare - 13.04.2011 ~ 8:30am ~ passed away naturally and peacefully in my arms