To give some news...
In order to do it in the best way, we are still waiting shirokun for the bass track...
Anyways, if both guitars were waiting for bass track, I think you can start to record your part without bass track. If you really need it, you might be able to do it using the "original" song.
About vocals, I don't know but it would be better that all instruments tracks have to be recorded.
EDIT: As shirokun doesn't answer in this topic yet, I'm going to PM him.
In order to do it in the best way, we are still waiting shirokun for the bass track...
Anyways, if both guitars were waiting for bass track, I think you can start to record your part without bass track. If you really need it, you might be able to do it using the "original" song.
About vocals, I don't know but it would be better that all instruments tracks have to be recorded.
EDIT: As shirokun doesn't answer in this topic yet, I'm going to PM him.