I used to let the shops do it because it would give me yards/capacity info but since then I've bought a bulk spool of 30# and eye-ball it myself. Cost a lot but it's like buying stuff from costco - buy bulk once and lasts forever.
IFFF Certified THCI @ 2005
Capeflyfisher Guide Service
Island Hopper, Guitarist, Incurable Dreamer
and Founder, Worldwide Flyfishing Forum