Yeah, I hear ya...you would have loved trying to figure out the settings in Vray 1.48 then! Made you feel more like a nasa engineer than a 3d artist..they've really simplified things lately.
But yes, that's why I always recommend moving the slider back to a default 'low, medium, or high' setting and starting from there. Then just change one parameter at a time doing a small region render to experiment and see if the change brings anything to the table (or takes away....).
I like to enable history in the VFB, the 'H' button at the bottom, then in settings enable 'automatically save'. Then each 'region render' you do automatically saves and you can easily look at the however many quick region renders you did and compare the time. Even if the regions are taking 15 seconds to render, you know if you change a setting and now it's taking 30 seconds...it probably going to adversly effect the time the whole rendering will take...
I was recently troubleshooting lighting in an interior kitchen scene. Render was taking +/-90 minutes. I did render region renderings around one can light and tried some different settings, then did a region rendering around a few other lights, then on to a region showing a cabinet and floor and played with some other settings along with sun/environment settings. Long story long: In 30 minutes of troubleshooting I dramatically increased the quality of the image and brought the render time down from 90 minutes to +/-30 minutes, or less depending on angle rendered. (I also added some fill lights to help with some darker areas, less noise to clean = faster render)
Remember every scene will be different and have its own factors so you'll always need to play with/experiment with some settings here or there. Good to start from defaults and tweak settings one at a time and evaluate them carefully....and don't be afraid to just reset to defaults and start over if you stray to far from the path....
Hope you're getting things worked out, cheers!
