Do you use Procreate for your design work? We have come across some great tutorials online teaching you how to use Procreate.
For a limited time, Screenprinting.com is offering their course for free!!! Sign up here: https://www.screenprinting.com/collections/screen-printing-online-course/products/designing-in-procreate
There is also this fantastic YouTube series on Procreate.
When using Procreate, make sure you setup your resolution when you START a design.
Make sure you set 300 dpi (or 600 dpi for really hi-res) to ensure your artwork contains enough detail. Again, this should be done when you first create the canvas. You will lose quality and start to see pixelation in the image if you increase the resolution after creating the artwork.