Customizing a new jacket!! + painting help

we're getting this totally awesome yellow denim jacket, i want to make a whole bunch of patches and pins for it <3 totally gonna paint it too! does anyone know if you /HAVE/ to use fabric medium when painting with acrylic on fabric? ive heard that heat setting it with an iron and/or using layers of hairspray can work, but im not sure. i also heard someone mentioning you can use glue and water as a fabric medium substitute?

i'll post pictures and progress when i get it in, it'll be my first big project like that! using it to learn how to handsew too :>