How to efficiently proofread my own mathematical paper?

A general technique, applicable not only to mathematical papers, is to list common mistakes, such as the one you noted. Then, you do a revision of your paper for each item on the list: reading only to look at uniformity, reading only to look if you introduce all notations, etc.

I've picked up this tip in the following book and it has worked well so far.

The book also suggest to reduce the familiarity with your text, so you might be able to read it as a "new" reader and thus find mistakes or parts that are not clear. You could do that by putting away the manuscript for a few days/weeks, printing it, changing the font, etc.

Another general technique to reduce familiarity is to read backwards.

Besides, if there is time, a break can help, i.e., not to look at the paper for a weekend, a week etc, longer the better, doing something else, and then reading it afresh. This context switch can help remove the bias of something having known already.