Tools of the trade...

The "traveler"...it makes measuring curves much more accurate.  Just place the arrow at the beginning spot on the item you'd like to measure.  As you follow the curves of your piece, count how many times the traveler goes around plus what ever portion of a full circle.  To be completely accurate, once I have my circle count with any extra, I roll it along a straight measuring tape the same distance and voila, I know how much straight material to start my project with.