The Down the Bay Race is one of my favorites. Did it a couple times double handing in Non-Spin. Remember the folks at HYC being great. We are slowly dipping our toes back into the racing scene and plan to do Down the Bay race in 2023, after some changes to the boat to hopefully make it easier for single and double handed sailing.
I would not recommend Down the Bay for someone wishing to learn short hand sailing. Down the Bay is more for those that wish to broaden the horizon and already comfortable short handed and sailing over night.
For the St Mary's Gov Cup or the old Annapolis to Solomons race you can get through the night on cold coffee and mountain dew (showing my age as I still refuse the new energy drinks). For Down the Bay you need to plan for 24 - 36 hours of racing, getting the boat to the line late morning of the start, and finishing at what can be a very busy port. You and your partner in the race need to be comfortable with single handing the boat in all conditions as you each will need down time.
Are you looking to jump straight into overnight short handed racing or do you already have experience operating a boat fully crewed racing, cruising, or day sailing?
Hard to provide specific advice not knowing the level of prior experience but in general start with the basics. Get comfortable getting boat in and out of slip, raising the main, reefing the main, tacking the boat and navigating shorthanded. If you are already comfortable with this, it more of a discussion on how to optimize to get the most out of your boat. How can I go faster than the next boat.