the inner tube works a treat, we used it for teaching stroppy yearlings. they would fight like hell but in the end had to give up eventually and they never tried again! please dont do the post thing i have seen this done once being reassured it was 'safe' well the horse freaked so much it jumped...
i had a similar experience with a weaner its mother had passed when it was younger and had to fend for himself so had no trust with other horses or people, this little fella would literally try to run head first into the stable wall to get away from me. one thing that proved helpful was just...