Yes, its possible. Once you have the receiver and one of the RF remotes in RF mode, remember its a two-stage process, first receiver and then remote. Once thats done, just do the following on the second RF remote:
1. directv device
2. press and hold MUTE & SELECT for two blinks
3. enter 0 0 0 0 1
4. press and hold MUTE & SELECT for two blinks
5. enter 9 6 1
6. press CH UP
7. enter the last 6 digits of the receiver ID #, found on a sticker in the access card compartment
8. press SELECT