I am not a chemist basically. I am a civil engineer. I thought the forum would be helping me in clearing my doubt.
Clearing doubts when it comes to some basic ideas is one thing, suggesting an analytical method for controlling the reaction progress, especially to someone not at least fluent in basic chemistry, is another.
A lot depends on the accuracy needed. Bromine test will tell you if everything reacted, can be good enough, it is pretty quick and very easy to do. This kind of approach was common even in the industrial scale installations back in eighties (no idea if they still do it this way, but I wouldn't be surprised). Sometimes you need much better accuracy though and/or continuous control, then you need to choose some instrumental method.