Thanks for the input Bannon. Yep, I eventually got the whole operation exquisitely timed. I chose to open a corridor on the German right flank as the various machine gun nests on the left have proven to be impenetrable. Still, I needed to spook the AI to think I was coming in on the left, so I probed with a single platoon over there. About 12 seconds after the gunfire erupts on the left my artillery starts hitting on the right. I do this because experience shows the first contacts are invariably met with a hailstorm of well-placed German artillery fire.
I snuck my right flank assault in as close as I dared -- a few units got shaken by the proximity of the friendly hits. The smoke was key for me and is the only way I could generate any kind of attack on Germans entrenched in the forest. Russians coming up from the beach have to advance over wide open terrain that is exposed to German fire from many different angles. If you get just the right smoke -- and there's no guarantee of that -- you can move them in close enough without getting butchered. Aside from the long range artillery that gets expended in 4 turns, there are two machine guns. The rest of the Russian units are infantry.
The reinforcements arrive in two waves at different points on the beach. They are not allowed to engage the enemy. Each wave has two machine gun units which are simply too slow to make it across the board in the allotted time. You might as well camp them on the beach and forget about them.
Since I'm trying to move the reinforcements off to the upper right, it is most disadvantageous that the second wave hits the beach at the lower left. They must make a diagonal traverse across the scenario or there is no possibility of getting them off by turn 20. And the last two turns they must run to beat the clock. They must start moving in that direction immediately when they show up, whether or not the forest is secured. The traverse, unfortunately, exposes them to well hidden German artillery spotters. So after killing every German unit in the forest, the Russian infantry must move quickly back to the center to hunt for these spotters. This requires them to re-cross the open terrain after all that brutal combat in the forest. Those German units do NOT go down easily. If you decide to forgo the second wave of reinforcements and leave them on the beach -- despite removing all the first wave units -- you will be awarded a major defeat.
In summary, I came up with a method to at least score a minor victory. It required lots of trial and error that gave me good knowledge of how the AI consistently deploys. In this scenario, I feel more like I'm learning how to beat a game instead of simulating something historical.