If someone is already in prison, is there a way you can still bail them out of prison??
From a prison operated by the Michigan Department of Corrections? Generqally, no ... because they are in "prison" for a circuit court sentence and the MDOC is not allowed to let the person out of prison without a court order or until the parole board grants parole or ther person has served the maximum time for the crimes.
But, if the prisoner has appealed something AND a court grants him an appeal bond AND there are no other prison commitment orders he is serving on other files not affected by the appeal bond, then it may be possible to "bond someone out of prison" pursuant to that appeal bond. But that is a very rare and odd set of facts.