GaRcfield.
I use a Great PLanes Accu-Throw meter ,GPMR2405, as well as a golf club "Loft & Lie angle indicator". This is a device, about 5" in size with two square magnetic sides and the remaining 180* is round with a 360* dial. You lay the flat side on the deflected surface and read the angle off of the dial. http://www.golfworks.com/product.aQ_...RO_A_cn_E_1894 Most retail golf shops or Dick's should have these.
Or a machinist's protractor. http://www.golfworks.com/product.aQ_pn_E_GP_A_cn_E_1894.
I use the meter or compass to set the original recommended throws, then adjust from then on with the (%) throws in the transmitter.

As I stated on the original post. Exponential is a personal preference. Less experienced pilots may need 30 to 50% to soften the thrown around the middle especially for those initial landings. Most advanced will use very little or no Expo. because they want imediate feedback and response. ie. Hovering.