Gloss clear coat canceling the capillary needed for pin wash?

Most clear coats that claim they are glossy; aren't very.

Let it cure, like you found.

Mattes of course don't work well at all as they get stained immediately and it can't be fixed.

You didn't say what pin wash type you use, but I get much better results with spirit based ones, like oil in turp, than acrylic.

Just me.

What Bill said. Plus a comment from me below.

JLKahn

The best I can tell is Clear Coats with a milkier thicker consistancy (and less prone to running) seem to have this problem, while clear cloats that are thin, but prone to running seem to allow for the capillary effect just fine.

Maybe you are laying on the thicker clear coats on so thick that you are filling up the depressions you were hoping to accentuate via capillary action wash?

I'll second what Bill and Greg both say.  I use Future as my clear gloss coat before weathering, and before adding decals, and the same advice applies.  It needs to cure completely (usually accomplished in 24 hours).  And it needs to be applied as a thin coat.  Too thick, and it will fill the fine detail so washes don't flow into the relief.

Glad to hear you're making progress.

That said, IMHO 'a few hours' isn't adequate cure time for any barrier clear coat with the intent of a wash on top.

BTW, thanks for updating your post to let us know what is going on.

In the future, I wonder if you might consider adding a reply at the bottom to update your comments or add more. I'm not sure everyone is going to see your update in your OP (original post). Hope that makes sense.