shave the  hair  & clean the duff off of it dirt & such ,  apply alcohol to the site & hold the iron on for  25 to 28 seconds if the wind is blowing hard 30 seconds . Even a home made ranch brand will work , use the edge of 3/8 flat iron makes a good brand . timing is very important . cattle with exotic blood have thinner skin 25 seconds tops . Done it for 30 years  . Good luck .