Fence Posts footings

I am replacing a wooden fence around my property. The posts are in ok shape but at least 15 years old. I am tempted to keep them because most of the posts are in concrete footings that age at way larger than I expected.

If I were to dig the out, each around one and half foot in radius and 24 plus inches deep, what are some good methods? I am trying not to rent heavy equipment but if I gotta I gotta.