It's probably on the can in the directions, but what is the ratio for the two components?

It's not on the can. All data for all paints no matter what manufacturer is available in PDF. It has to be. Note that reduction is optional. And reduction is the same for non lead-free. https://buyat.ppg.com/refinishProductCatalog/ViewProduct.aspx?ProductID=c98c3f28-89c5-467d-9983-e87c240f4c09

2:1

as in two part DP90LF to one part DP401LF or 402LF

of course i just pick DP90 black as an example.
for use as a sealer add one part of your favorite DT reducer, (dt860, dt870, etc)