I’ve been planning to get a pickguard blank from Warmoth and replace the one on my Cyclone.
I’ve got a regular hack saw and coping saw and plenty of sand paper.
That's a good way to do things.The "best" way is to use a router table using the old pickguard to make a template for the new pickguard and then using that template to alter it as desired and cut the new one. You will also need the extra height of the template to be able to use a chamfer bit to get the 45 degree edge.
Saws and files can work but it will be very time consuming.