You can’t consolidate federal with private, but you can consolidate each of them separately. Your private consolidation loan interest rate will be based on credit history, so have a cosigner with good credit can help bring the rate down. Sallie Mae consolidates both types of loans, so you can manage them in the same place:
federal student loan consolidation:
private student loan consolidation:

Yes, BUT the end result will be a private student loan consolidation, which means that your Stafford Loans, which you could consolidate as a fixed rate federal consolidation, will be in a variable rate private consolidation - and unlike federal consolidation, private consolidation has NO CAP, which means rates can go as high as the indexes they’re based on.

Good luck!

Christopher S. Penn, The Financial Aid Podcast
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Yes. Go to Nelnet.com

I don’t see why not. You just apply for a loan and use the money to pay off your Staffords, then pay the loan.