You don't really crimp a wire to another wire.
We crimp PWM pins onto the encoder wires, slide on a 1x5 housing (so if we ever want to use Jaguar closed-loop feedback we don't need to modify anything) and use a custom-made splitter cable to bring the signal to the DS. All the supplies and tools we use for this process come from
Hansen Hobbies. It takes a bit of practice to crimp the wires properly, but it's well worth it when you finally do get the trick down. I personally prefer it because it keeps the wires clean.
Soldering is a quicker and simpler process, but take care to ensure that you don't damage the encoder wires whilst doing so; also remember to properly insulate the connection.