It does get easier with practice. I hope you have jacklines, a harness and tether installed on the boat, since you're single handing. The primary thing about single handing is to stay on the boat.
BTW, just be aware that the cockpit lazarette locker really needs to be dogged shut when you're sailing a J/24. The lazarette locker, if it isn't dogged shut, can downflood in a broach or when heeled excessively, and fill with enough water to sink a J/24. It is a fairly common cause of J/24's sinking.
I didn't tie in that day, but I will be in the future.
As for the j/24 tipping and swamping. I do keep the lockers locked, and the hatches closed. And, you may find this humorous... but I've been saving and storing 2-liter bottles in all the unused space below deck. I also bought a great used air mattress to sleep on, rather than foam (a steal at 8 bucks). I don't have 33 cubic feet filled up (enough to counter the j/24 weight) with these free flotation devices yet, but I may get there