To guide you through the whole import process I made this step by step tutorial :)
1. Open the ControlCenter on your iPad/iPhone (swipe up from the bottom of your screen).
Activate AirDrop for "Everyone":
2. Select the brushes you want to import from your Mac.
Choose "Share" > "AirDrop" from the right click menu:
... OR drag & drop them on the icon of your device in the AirDrop folder:
3. The selected the brushes will automagically appear on your iPad:
After the transfer is complete, choose "Open in..." > "Procreate":
Success! You'll find all the new brushes neatly combed in your "Imported" folder:
Tip: After importing a brush set, just rename the "Imported" folder (e.g. "Oil Paint").
For the next (batch) import a new "Imported" folder will be created.
This allows you to quickly import different brush sets without moving the brushes manually from "Imported" to their respective folders.
If you have problems using AirDrop (like I had after updating my MacBook), this video shows you several ways to fix it:
I hope that helps and wish you happy air/brush dropping ;)