Rendering study (rainy/moist shader) — looking for advise

Hi, I'm a compositor and trying to learn Clarisse to get deeper into the shading/rendering theory and also get some shots for comp practice.
As a test scene I've decided to try to make a heavy raining environment with some cars in it. Something inspired by final race from "Ford vs Ferrari" movie.
For now I'm using very simple shader for the wet surface:

All materials needs improvement of course. But the main problem I faced with right now is the path tracer's settings.
Turned out (how unexpected, though /s), that render a surface with tens of thousands small sparkling raindrops in contrast light is quite a feat to achieve, both for render and artist.
Here is two last version I've got so far. (You can open fullres in a new tab and I can upload EXRs if you curious)
v04:




I figured out (mostly thanks for the great tutorials and sometimes empirically) that it's better to use a Standart Deviation for Refinment Variance (since I have raindrops virtually all over the frame, and Splatting anti Aliasing Filter Mode (same reasons).
With this settings on my PC (i7-6700K, 32GB RAM — I know, that it's pretty weak for the task) it takes roughly about 1hr per image. Though quality isn't to high.
And then here is v05 with higher sampling settings:




It looks much better! I already could fix the rest in comp (everything is gonna be much, much more misty in the end anyway), but It'd still be nice to get better results from render if possible. The problem is now it takes about 5hr per image to render. And I absolutely not sure if I'm doing it right.
So if you have any thoughts (or advice) to share on the rendering/shading setup (or whatever else it could be actually) I'd love to hear from you! Or is it only brute forcing left to me?
Thank you very much!
As a test scene I've decided to try to make a heavy raining environment with some cars in it. Something inspired by final race from "Ford vs Ferrari" movie.
For now I'm using very simple shader for the wet surface:

All materials needs improvement of course. But the main problem I faced with right now is the path tracer's settings.
Turned out (how unexpected, though /s), that render a surface with tens of thousands small sparkling raindrops in contrast light is quite a feat to achieve, both for render and artist.
Here is two last version I've got so far. (You can open fullres in a new tab and I can upload EXRs if you curious)
v04:




I figured out (mostly thanks for the great tutorials and sometimes empirically) that it's better to use a Standart Deviation for Refinment Variance (since I have raindrops virtually all over the frame, and Splatting anti Aliasing Filter Mode (same reasons).
With this settings on my PC (i7-6700K, 32GB RAM — I know, that it's pretty weak for the task) it takes roughly about 1hr per image. Though quality isn't to high.
And then here is v05 with higher sampling settings:




It looks much better! I already could fix the rest in comp (everything is gonna be much, much more misty in the end anyway), but It'd still be nice to get better results from render if possible. The problem is now it takes about 5hr per image to render. And I absolutely not sure if I'm doing it right.
So if you have any thoughts (or advice) to share on the rendering/shading setup (or whatever else it could be actually) I'd love to hear from you! Or is it only brute forcing left to me?

Thank you very much!