I have single handed much of my sailing days. When I need to pick up a buoy I arrange a mooring line from the bow outside everything back to the cockpit with a big carabiner on the end. I then pick up the buoy from the cockpit, attach the line and sort things out at my l own time.
If it is windy run the line round the rope drum on the windlass before taking it out the bow roller.
I have used a device like the happy hooker in my early days and it worked well if the buoy had a nice ring on it, much less well on a loop in a line.
Also I had a device that held a giant carabiner but nowadays just use a regular boathook and manually attach the carabiner as I find this to deal better with the wide variety of mooring buoys and their attachments out here in the Caribbean.