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Someone else might comment if a guitar is a preferred option for playing, as it's quite different.
I am a guitarist so this might surprise some people but I would start with a MIDI controller keyboard as Gordon and David suggested. Why? Well with a guitar one must build up calluses (this will take some time), coordinate the fretting hand with the pick holding hand, and somehow get the chords/leads into BiaB. With MIDI keyboard one can just presses a key(s) to hear a note(s) and to have it recorded into BiaB. If one gets a piano chord chart or book, google/bing
piano chord chart and you will find a number of free charts like this
https://www.onlinepianocoach.com/support-files/chordchartforpiano.pdfand one can play the chord using a MIDI controller keyboard and BiaB will recognize said chord, at least that is what I am lead to believe. If I am wrong please correct me ASAP.
I believe that using a MIDI keyboard controller would be must faster and easier than learning the guitar when getting chords and leads into BiaB
PS - I know there is a learning curve setting up a keyboard controller and using MIDI but that is still easier then getting a guitar part into BiaB IMHO, YMMV