How do you use a Brix meter?

I recently bought a Brix meter because I thought it made sense for my vegetable garden to gauge my veggies and their sugar content, but I've been told by many that it can be used to determine the harvest time for our plants. This may sound stupid but, with fruits, I just take some of the juice and drop it on the meters' well. How would one take a measurement from a bud where there's no juice to speak of? Of course I suppose one could simply take a bud and blend it until it's liquified but I think there has to be a better way right?

Secondly, how does this tell you when harvest time has arrived? Do you have to take continuous daily readings during the last week or two of flower? What kind of readings are you looking for?