For the most part, just a matter of practice. One advantage that it has is that you have less incentive to make multiple simplifications in a single step. Copy a line, make a rearrangement. Copy a line, combine two like terms. Since you aren't re-writing everything that is unchanged, there isn't as much of a cost to showing your steps.
I did get a rather funny look from a professor in grad school when I turned in a fully typeset document on a timed take-home exam.
I had a few professors require LaTeX solutions. After a little practice it was only slower than handwritten answers for some symbol-heavy assignments. So much time was spent comparatively on solving the problems that it was a negligible overhead regardless.
