What's the best way to deal with a relative who seems to have a financial crisis every other week ?

Tell him your sorry for his plight but you are unable to help him. Say NO and mean it. Once you break down and continue helping it will continue.

Let them find a solution to their problem.

Ignore their whining

Never lend them any money. Unless it is for life saving medication like insulin.

I have bailed my ex out a couple times when they ran out of insulin but for nothing else. If they are out of groceries, they get no money. I give them food instead. If then need a car repair, too bad. A car is not a necessity of life. They can see a payday lender.

By saying you hope they can work out their problems.

It is not your responsibility to bail out people who are too irresponsible to manage their own lives. Once you start 'offering to help', such deadbeats will invariably think you are now their personal ATM.

If you want good answers, please provide the details.
What is the relationship between you, etc. . . .