KIP HELP! (gymnastics)?

I can do a kip by myself most of the time but I always tap my feet & bend my arms. & sometimes (this is kind of funny) one of my hands slips of the bar.... My coaches always say stuff like "lock your arms so they don't bend." & they say "don't tap your feet" but the problem is that they're not telling me how to not tap my feet. so could somebody pleasseeee help with these problems?