One thing you can try is to make a test print which gets your mids/highs to where you want them. Expose for that time, but have hot, undiluted developer available. Pull the print (early in the development process), place it on plexi (or glass) and paint the shadows with the hot developer. You can use a soft sponge, cotton balls, or Q-Tips. It will require some testing, as the highs/mids will continue to emerge while out of the tray. You'll have to figure out when to pull the print, so the highs/mids don't move past where you want them in the final print, but it will get your shadows to go darker quicker. Not an elegant solution, but it may help in this case.