Quick (I think) question about multi-channel transmitters

I apologize if this is the incorrect forum to post this question under, if it is if someone could please kindly point me in the right direction that would be superb.

My question is this:

I want to make a radio control car; but I want to design and code all the brains myself.

For the transmitter I only want two channels, one for acceleration and one for steering. I'm a little unsure how to pull it off however or how this is generally done in an rc car radio I could buy at the store. Do they actually use separate frequencies for both channels, and if so does this require multiple antennas? Or, do they use an addressing scheme and one frequency and the receiver looks at the "address" to determine which channel has sent the transmission. It seems, especially when you consider larger channel rc plane radios, that the addressing scheme would be most likely as too many channels means you could quickly leave the unlicensed bandwidths, or am I way off?

If an addressing scheme is used then I have to make sure that my clock rate is high, and that my code is efficient for everything to appear as though it's working in real time as opposed to switching between accelerating and steering, correct?

Since I already own linx technologies HP3 transmitter and receiver from a school project I was planning on using those to build it.

Thats it; again, sorry if I'm in the wrong place. Thanks for your time and help whether it be in regards to my question or simply pointing me in the right direction.

- Johnny B