I was just throwing out an alternative to the "vacuum route". You can still try your original option.

Use the advanced search option on the forum. There are multiple threads in there of things people have tried that worked. There are also examples of things people tried that didn't work, and they give the reasons.

I am a big fan of experimenting when attempting novel (to me) projects. Maybe go pump a little muck out on some nice weekend. Install a little row of silt fencing to filter and catch the debris. See how easily you can clear a small area.

After you get that info, I think you will have a much better idea of what modifications are needed and you can plan properly for when you are ready to perform the big job.