Controlling Analog RC Car Remote with Arduino
Don't emulate it. Just go digital. Use a Digital Potentiometer. Some use i2c some use spi, some have a serial input. Just pick one with the same resistance range (Say 50k or 100k), and try to pick one with a high number of steps (different positions between the high and low ends of the potentiometer range). You can also get them in Log or Linear version.