Saw H41 streaming yesterday and popped in. People asked a few questions about LG, so I asked the most basic question, and H41 went above and beyond in answering. In the video he covers the concept of short-range LG, the technique he uses to train his teammates, and even points his camera down to show his arm/wrist movement. I've summarized everything below.

Don't focus on your percentage. It means nothing since it always changes depending on the situation. If you really want an accurate representation of your raw accuracy, use Eye to Eye.

Learn to use LG with two stages of training: close-range, then medium-range. Practice each stage for at least two weeks to develop a good feeling/grip of your mouse movement and dodge. For short-range LG, practice on the bridge in Asylum or in Trinity's tunnel because it forces short dodging patterns and something H41 calls K aiming. K aiming uses left/right strafing with some +forward mixed in. After 8-9 days of practice, you'll develop a sense of using the movement pattern to aim for you. Now begin using your wrist--not your arm--to make micro corrections in line with your opponent's dodging. Doing this will teach you to hook your opponent.

In this first step, train only 1v1 CA, not 2v2, not public CA games, et cetera since in these modes you spend too little time actually using LG. In the video, he plays one round with K aiming only (hits 51%), then plays the rest with micro corrections added (hits 63-66%). Against players with a good dodge, H41 hits 50-55%, and he considers 45-55% a good result at the end of your training.

In the second step of training, you'll learn to move in larger spaces. On Thunderstruck or Drunken Mummy, train with 2v2's, not 1v1's, so that you learn to learn to hit your opponent while he is not watching. From this you will learn positions in which to place yourself. In another stream, he'll explain more this second stage of training.