I will note that I’m not an expert in the plethora of USB charging standards. Quite frankly, USB C is almost like black magic to me. With that said, finding the D+ and D- lines might be tough unless you’ve got a USB C charging cable you’re willing to cannibalize.

That is, what you can do is carefully splice into such a cable, then connect it to the board and a USB charging block. By probing the wires, you can rule out the power wires, which should leave you with the D+ and D- wires. You would want to do this with a cable that’s meant only for changing, such as USB C to USB A. That way, there would only be four wires inside. If you cut open a USB C to C cable, you’ll have a lot more wires that you have to check.

Once you identify the D+ and D- this way, you can then do continuity checks from those wires to various pads on the board. In this way, you’ll eventually find your D+ and D- pads, and can then add your temporary resistors, to see if that works.

As for identifying the USB charging spec in use, that’s going to be tougher. I think there are test devices that take the place of a USB charger and can display or change the spec, but I’ve never used such a thing.