[Roadsters] brake flushing

[Tim]

I want to flush the brakes on my SRL. And I want to put the best recommended fluid back in. I do not know what fluid is currently in the brake system. I may be able to find out if I can find the phone number for the previous owner.

My questions are these:

What is the best way to completely flush the entire brake system? 

And

Does it matter what fluid I put back in if I do not know what is currently in the system? I would hate to put in fresh and find out it is not compatible with any possible remnants of the old fluid. 

TIA from rainy southern WI.

Tim
Belleville, WI.
'70 SPL AND SRL
Still clueless but always learning