Hit youtube, plenty of wax slug experiments documented for posterity.
Crayons work great, the only problem is the slugs aren’t spin stabilized and start tumbling within a few tens of yards. Not a material problem, they hold together fine, rather a physics problem.
Modifications almost always come at a steep price of effective range reductions. For example, the infamous “dimes” round.
There is a video on YouTube testing a round filled with dimes, but at a normal short distance range. And it’s not surprising that they were disappointed in their performance, because dimes are a very short, even point blank round.
However, I know of an instance in which an older woman very effectively used a dimes round against an armed intruder in her home, at very short range, and the results were impressive, to say the least. When the police arrived, they had no idea what had shredded the robber, until they noticed bloody dimes scattered about.
(At some point one of the officers got sick to his stomach.)
To her credit, the old woman had the chutzpah to ask could they please return her dimes after they were done, in that they were “lucky” dimes.