ADR can be accomplished in many ways for indies. The simpliest would be to playback the video clip on your computer, point the camera's mic to your talent's mouth (but I prefer the chin as it minimizes a lot of probs), do lots of rehearsal then start rolling til you get what you need. Don't forget to playback after your first recording so you have an idea on what you're getting.
Sorry, I don't get the question on the DAT recorder and clapper. Please be more specific. Do they also use a camera during the dubbing session?
Anyway, in essence clapping the slate is necessary only for SYNC audio shooting. The clap isn't necessary on MOS shoots.
Most of you guys know this but I'll say it anyway hoping a new Clapper will be helped. The slate is used for two purpose, first, for clip identification and, second, the clap is the guide for audio synching.
In our productions, the slate is given importance as it helps a lot during post. The camera operator makes sure that the info and the clap is visible. And the clapper announces the info on the slate before he claps the slate. We usually put as much info on the slate as possible. We also apply back slating after important takes, for notes like GOOD TAKE or ALTERNATE.
By the way the slate we use is only a piece whiteboard with a wooden stick attached to it. We pasted small colored papers (Blue, Yellow, Red and Green) at the back of it which we use as color guide during color grading (we shoot this for every lighting setup). It's a little bigger than the usual as we put in more info. It's working well for us so far.
Didn't mean to brag, just trying to be of help.
Best regards...