I am in the process of adding larger diameter breather vents to my valve cover. i've seen others do it and am looking for tips and pointers.

There are baffles inside, what do you do to clean out the chips after drilling the larger holes?

Also, the factory breather is close to the top edge. To put in a large diameter fitting you need to locate the center lower than the factory port. This makes drilling the hole kinda tricky. Any tricks for this other than a milling machine.

Here's an example.