Also a Hobby painter here,
Tom is right on his suggestions. Currently available thinners will work.
The slowest thinner is DTL 105, I believe..
Sealing the modern paint is critical. Laquer will try to eat into the lower coats and cause all kinds of problems..
On my Roadrunner I used the DP epoxy primer with the textured Laquer on the dash, good results..
For the hood, I used the Concept version of Organisol, (DCC) on top of the clear coat with no sealer it came out looking good as well.
I didnt want to risk the laquer on top of the modern paint.