Yes, absolutely. In fact, if you have your second brew ready at the same time that you pull the first beer off the slurry, you won't benefit from a starter - just use the whole slurry for your second batch.
If it will be a week or more between batches, then I'd recommend using the yeast washing method described here: Yeast Washing Illustrated
Not sure I would use the yeast from a keg. I may be way off base but the best yeast would be from the primary.. more flocculant etc. Can anyone correct me if I am mistaken?