Battling a Self Employed ex

Can anyone give me their story of battling a self employed/business owner ex?
I am struggling to understand what it is going to take to expose his income for what it really is process wise and what’s it going to cost me.

Any stories, good or bad outcomes, would be appreciated.
Thanks

FYI, this is in regards to determining income for child support. Not a divorce.

Look into hiring a forensic accoutant. they can cost a little or a lot depending on the amount of work they have to do. I am considering the same thing.