Old metal radiator restoration

I got it pulled from my 1980 truck. It's heavy. When it dried, white chunks came out of the return when I shook it. There is also coolant stains on the outside here and there. I'm pondering taking it to a pro. But I have the means to dry pressure test it. And I thought of soaking it in radiator flush and then hosing it out. Was cooling fine and I wasn't adding much coolant at the time it was pulled. What's a good product to flush it? Any direction on how to deal with it is appreciated. Sorry if this has discussed in detail before.