Thanks guys for all the replies!
I guess I didn't give Z2+ZFX enough time to cure before buffing..(15~20 min for the first two layers and 30 min for the last layer)
Hmm...I will put another two layers this weekend if my knees feel better!
Zaino is so easy to apply but still hurt my knees....
Since I am going put just two more layers...
If I only use 0.5 once of Z2 how much ZFX do I need to add in?