To anyone looking to start casting keycaps or get into artisan making, please don't let anyone discourage you. While it's definitely a daunting project to take on, it's not outside the grasp of almost anyone here, and the end results are very rewarding in my opinion. Do your research, be safe, and you'll have a great time.
I see established and random makers telling others starting out that they're making molds incorrectly because they're not 3D designed, or because they use qtips for sprues, or they're not using the resin/silicone that the 'maker' recommends. This is not incorrect at all. If you find a method/process/materials that works for you, and produces results that you're happy with, and that's safe,
**** what other people are telling you, you do you.
There's more than one way to skin a cat, don't let these clowns tell you otherwise.
PSA Over.
Here's a compilation of guides/tips/tutorials/supplies for casting, run wild.