I would add the sweetener to taste, and add extra liquid if it's too thick, or simmer it a little longer if it looks too thin. (cookeatpaleo.com)
Then add small amounts of extra liquid as need to get the blender running smoothly. (kaleandtequila.com)
I always buy those big packages of broth and use it several times You might want to add a little extra liquid if you are going to be gone all day. (familyfreshmeals.com)