Slicing bratwurst for quicker, more even grilling
Boil or steam them using beer (for a traditional flavor combination) or water before grilling. Grill for flavor, not as the sole means of heating them. 

This is more about cooking faster (or more evenly, anyway) than slicing, though that step will also make them hold together better if sliced after boil/steam and before grilling. But if they are basically cooked via boil/steam, you don't need to do any further processing before grilling, since you can just grill until the outside suits your sense of grilled. 

I think scoring is more about releasing some of the fat than actually grilling faster. Slicing (like in half lengthwise, or in chunks) will grill faster, and/or give you more grilled surface area/flavor (if you're pre-boiled and just grilling for flavor.) It may fall apart completely if not cooked somewhat before that.

This site looks reasonable: https://www.bratsandbeer.com/how-long-to-boil-brats/