Any hints to score a reservation on Recreation.gov

Two summers ago we planned a vacation to Door County WI and wanted to stay at the state park there. I monitored the reservation website and found that sites would be taken the first few seconds the reservation window opened each morning. My wife, daughter, and myself sat on our laptops and started to attempt to make a reservation a few seconds before the window opened. It took 3 days of trying but we finally got a site. Some campgrounds are just that popular.