Suggestion number one:
Learn Calligraphy! It's a lot of fun and does mean that you can write the fonts in genuinely nice ways. Books on calligraphy tend to have detailed instructions on how to do at least the basic alphabets: explaining which stroke to do first, and how to hold the pen. Although not all of it transfers to the blackboard, it helps a lot. For example, once you seen how the different "g"s are written, you'll know how to write the Lie algebra symbol correctly. However, I do find that a script S ($\mathcal{S}$ is not even close) can take me a couple of goes to make it look right - it shouldn't be pointy at the top but should sweap backwards.
(Note: to anyone reading the comments, I originally had this answer together with my other answer in the same post. Given the comments, I decided to split them.)
Following up on aleksander's comment to the original question, I had a go at doing a video of how to draw a fraktur g (𝔤) (well, actually it's gothic but if you know the difference you don't need this video, and the gothic g is probably more distinguishable from a normal g than a fraktur one on a blackboard). It's not very polished, but you can see what it looks like here. It was quite fun to do so if this would be helpful, I can easily do more.
