Screenshots of what you're doing.

Yeah, kind of brush overlay (func_door/wall/whatever) with different shader could do the trick. But it's all hax, dirty, dirty hacks.
I'll better start learning start learning about C and QC. Despite the amounts of time it may take, there is no other pretty way around. An engine should have it's flexibility, and what we have here for level designers is naught but same old good Quake-styled entity manipulations. Graphics were improved, game mechanics were improved, but they're not really tied together as they should be.
Maybe I don't know much about the DP engine, reasons for this and that, but again, I'd better inquire the roots of the problem and see what can be done rather than train my trickery trying to do something that engine isn't designed for at all. This is lot of fun, yep, in past I had spent lots of time doing same perverted stuff in various Half-Life mods. But it's not serious at all, trying to squeeze last drops out of old engine rather than implement the stuff you need.
I'm not forcing anyone to help me, just my thoughts on that.

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Do other compilers support that? Maybe hmap2 does.

I bet he meant engine map format itself there.