Ohio was the last state to place the burden of proof on the defendant for self defense, and I believe the law changed there either in 2020 or 2021. In Wisconsin, the burden of proof for self defense is on the prosecutor to disprove beyond a reasonable doubt any of the elements of the defense.
For all other affirmative defenses, you’re correct that the burden is on the defendant.
Why not look at the Wisconsin Jury Instructions?
https://wilawlibrary.gov/jury/files/criminal/0805.pdf
https://wilawlibrary.gov/jury/files/criminal/0805A.pdf
There are others here:
https://wilawlibrary.gov/jury/criminal/instruction.php?n=820