New Brewer needs help - Carboy Use
That does sound like a good idea. I've learned by using glass carboys that when the beer clears in the primary it's getting close to being done, and airlock is down to nothing. I then transfer to secondary and take a gravity reading from sample. I'll wait maybe a week and pour another sample and if it's close to previous reading or if it is close to bottom of ranger for style I'll go ahead and bottle.
The stout I just made was at 1.020 after fermenting a week. I transfered to secondary after about 4 days from first sample and gravity is the same. no activity at all in airlock so I will bottle it this weekend. I added a pound of lactose so that is why the FG is where it is. Tastes fantastic.
Also when I bottle it I am going to use cartabs for the entire batch. I liked the results using them on part of a batch. Also they seem to carbonate faster than using sugar. So I can enjoy the fruits of my labor sooner. 
DC