Reticulation looks much different than big grain. If you want to reticulate, I'd try soak in a strong, hot alkali to swell the emulsion then soak it in room temp a strong-ish solution. I only did this once, but it worked pretty well. If you want to have big 3200 grain, use 3200. You can get enough filteration some combination of ND filters, polarizer, and a red filter. Or use lith if the color works for your image.