We released a new Add-on called Schematic Tools.

It allows you to bind saved brushes on any minecraft tool which can also be a custom item of any type. This item can then be given to players which will allow them to use this specific brush bound to the item. This works even when they do not have access to schematic brush itself. They can also use the preview. Tools can have a usage limit and a dedicated permission if you want to restrict access a bit more.

Get is here:
https://www.spigotmc.org/resources/schematic-tools.103776/