They sell a tape for this, when you hit the ball it leaves a mark on the tape.

Get some beige masking tape (painters tape) with the grey label. 

Works like a charm. I've used it for years. No mess, and works for multiple hits. Strike, lift and reapply if you want a reset... It works for a few shots, is cheap, makes no mess unless you litter. You can use it at home if you hit inside...

You could also use a dry erase either on the club or on the ball (leaves a mark on the club), which works, but I think tape is better. 

Good luck!

Mike , how did you make out?

Will have to try this! Thanks for the info

I use Dr. Sholl's Odor X on my clubs for impact testing.  I learned that trick from Andrew Rice---teacher at Berkeley Hall in Bluffton, SC. 

Much easier than impact tape...just spray on...hit a few balls...wipe off. 

If you happen to not wipe all the foot spray off and say leave your clubs in your trunk for a few days that stuff turns rock hard! 

Only thing I found that dissolves it is laundry detergent. Put some on the face, rub it around with your finger and it will wash right off!