It's a recommended tutorial for learning Java and then modding Minecraft. I would use GIMP 2 over Paint, mostly due to transparent backgrounds being possible. MCreator is currently the only mod creating software that I am aware of - and it's not very good compared to programming a mod by hand.
you can help with textures and other stuff textures are kinda hard for me becuase i cant get them right without messing it up
i used custom npcs to make a textured boss and the texture got weird like the texture was off where it just bugged and only lines of the emerald block texture messed up on my boss thats why i suck at mod textures