That's exactly why I bought BIAB -- to add bass and drums (and other things) to my songs.

So you pick an appropriate "style", pick a tempo and key, add your chord progression (and sections) and voila, you have a backing track for your song.

Picking a style is a trial and error type of thing and you can change it down the road if you need to. Once the BIAB song is done, you follow it and play acoustic guitar and sing. It takes some effort to make the song exactly the way you want it, but it is reasonably easy to get 90% of the way there.

I only use BIAB for original songs and I compromise with BIAB to get the song done -- but it mostly ends up the way I wanted it to. Feel free to peruse my BIAB at the link in my signature to see what I do with BIAB.

Now at bandcamp: Crows Say Vee-Eh @ bandcamp or soundcloud: Kevin @ soundcloud