Have a look through the multitrack tutorials I did awhile back.
Stuff like Anatomy of a Multitrack etc...
Usually what I'll do is record the background music first, then I'll use a track to just sing a lead vocally. (put on some headphones, turn it way up and really get into it if ya know what I mean)
It's easier to improvise an idea for a solo if you aren't paying attention to what your fingers are doing, or thinking about scales and stuff.
Then listen back to what you sang and learn your own solo a few bars at a time.
I can't remember exactly which tutorials they were but I did a couple of examples of singing a lead and then redoing it on guitar.
There's also a trick you can use by recording a lead on multiple tracks and then joining them together.
You'll probably find some other stuff that'll be helpful too cause I went through the whole process of recording a song one instrument at a time, adding the solo, writing the lyrics and doing vocals etc.