If you like to eat natural peanut butter, such as Smucker's brand, you probably know the big problem: you have find a way to stir the separated peanut oil back into the settled mass of semi-deoiled peanut butter. The least messy and most reliable solution I've found is to use a old Rock Tumbler to stir it back up.

Supplies

1-Jar of Natural Peanut Butter (Creamy)

1-Rock Tumbler (eg; Lortone Model 33B)

Step 1: Quick Tips

Generally 1 to 2 hours of tumbling does the trick
Optionally, turn the jar upside down for several hours before tumbling to get the oil layer closer to the middle or bottom of the jar
Monitor the jar during tumbling to make sure something bad does not happen: Yuk!
Note: I have not tried this mixing method yet on chunky style