Basically I want to go through all my songs and send good ones to the same playlist. What's the quickest way to do the sending (rather than right clicking an item, selecting send to playlist, selecting the playlist I want and clicking OK)?

Anyone got any suggestions?

Set a shortcut to do exactly what you said above via the keyboard shortcuts in the preferences.
Edit: actually use foo_utils so that you can set the shortcut to the actual playlist not just the dialog box to select a playlist.

you can use Album List plugin or panel, with dbl click or middle click action: add to playlist.

That bit was exactly what I wanted to hear! Thanks!

I just set it, up, but is there any way I can make it not change to the playlist the songs are being sent to? I have to keep changing back to the database after each add.

I think this should be possible in 0.9, but don't know if foo_utils does this in 0.9, I'd try it out, and if it doesn't maybe make a request from foosion to add that capability.

Edit: OK, I just tested it, there is an option to prevent switching to the playlist in 0.9, or you can hold shift while sending and it won't switch. If you don't want to switch to 0.9, I would just download it and use foo_utils to make a playlist, then save it somewhere, and load that fpl into 0.8.3.