"Four Feet Means The Horse Only Defense TOOL"
The reason we say young foals must be Imprint Trained is this and the 4 legs must be Desensitized right after birth unfortunately many don't do and come to a point that might hurt themselves or the poor Horse and many think this is the work of Farrier which is not.
would we give up our only defense tool to someone which we have no relation no Bond , Trust and Confidence?
Stay out of the kick area and be aware of it.
The only Defense Horses have in time of danger is their legs therefor you are asking a Horse to give up their only defense tool, so you have to be patient.
Grooming is very much important because the Horse logical Communication starts with Grooming but start in a sensitive way make each session short take some steps back pause then go to the horse praise then restart your grooming this is very important to make your sessions short and take some steps away from the horse.
Start with grooming Establish Trust make good Bond and Gain their Confidence.
Desensitize each leg without picking them up just rub them until they are fully Desensitized to the touch of your hand.
After Desensitizing just very lightly clap each leg by your hand normally after some clapping they pick that hand up when they do Hold the hand for few seconds and let go don't hold the hand or leg too much.
Is best to leave the Horse after each session and take some steps back so they know you are no harm to them.
If the Horse is holding his/her head up that means you wont be able to pick any hand the horses head must come down (normal position) this means the horse is calm while you are with him/her ? if not start with grooming again and be more patient and give more quality time spend more time with the horse , lead properly too.
If you are not so sure that you can desensitize the 4 legs by your hands then you can make an artificial hand to especially doing this and Desensitizing the 4 legs.