Just my $0.02 having put in with varying levels of help (experienced vs "rope holder" lol) in a public and busy ramp for a few years:
1. Find the most available slip to put into where the boat can be tied to 2 cleats on the dock and blow downwind without hitting another boat or dock while you go and park your vehicle / trailer.
2. Have the mast stepped and sails up before putting in. This would mean with the trailer still connected to your car for counterbalance. Step the mast solo using the gin pole method and a hand or electric winch - this can be tricky, but YouTube is good!
3. Keep your rudders up and your jib and main sheets loose so the sails can luff downwind while your boat is tied to the dock and you're parking the car/trailer.
4. Slowly back the boat into the water and have your 2 ropes ready for your cleats. Launch the boat with the ropes long enough to be in your hand and around the cleats as well so you don't lose the boat or the ropes. Once the boat is off the trailer, still holding the rope(s), hope up onto the dock and pull the ropes in and tie off so that your boat is held away from the dock a few feet with the wind. Now park the car and trailer and come back.
4. Disconnect the rear most rope from the dock and toss it onto the trampoline. Disconnect the front rope and hold it in your hand. Walk it as far out on the dock as you can go, then pull the boat close, hop on, and do your best to drop the rudders from there and paddle/ tack out to where it's safer to pull in your main and start sailing
We usually put into a ramp with only 2 slips that's tucked in a cove on a lake. It's tight quarters, there are power lines, and usually a long line of boats waiting impatiently lol. If I can have all the rigging and sails in place and all I have to do is launch, I'm usually golden. The mast stepping is usually the doozie for me though...
Hope this helps or at least gets some gears turning. Of course there are more experienced people here than myself who could probably tell you better, but just my $0.02.
Good luck!