If Im recording a second track i try to play a different part that accents the first. Usually second and third parts are subtle yet fill the space with similar chords in a different area of the fret board or a complimentary chord. If i just want a wide sound I double the track , pan left and right and off set the the tracks by the smallest of time margin and it widens out the entire sound. My guitar has three pick up settings so I'm not shy about switching to neck pick up, bridge pick up or both and playing with the volume and tone knobs till i find something i like. I also have a solid mahogany and a solid maple guitar and they sound entirely different due to the wood and different pick ups. The trick for me is to find something different to play that compliments the mix and sits in its own place in the song with clarity. But it can be done with the same guitar or even the same mics and different effects. Its about experimenting with sound till you find what you like on the second track. Most of my second and third tracks alone lack the context to fill a song but they compliment the main riff so much that it sounds naked without it.