However you do it the most important volumes are pre boil and post boil, along with the gravities. It helps to see where the final volume should be while you are boiling so you can turn down the boil (or cover the boil kettle) if you approach final volume too quickly.
I read an article in brew your own mag about etching your kettles, was going to do it then I found an old metal engraving tool and just used that to mark graduations on all my kettles on the outside. Makes the brewing day easy. Eventually would like to get sight glasses for all but yeah, too costly and makes for more things to clean, and have to be careful when handling kettles not to break them off or loosen them and get leaks. Still have to use water and graduate /mark the glasses when installed...
For losses I just pour what's left in the kettle into a graduated 2 liter tupperware container and measure, hopefully not more than once. Hopefully there isn't enough lost wort to accurately measure with a stick or kettle markings, especially when measuring loss from fermenter into bottling bucket or kegs.
