There is no "one size fits all" way of establishing pasture or hay where desirable grass is already mixed with undesirable plants. If the land has net fence,alowing someone to run goats on it is a good start. Goats eat weeds and brush but very little grass. First question is whether there's any desirable grass amongest the hih weeds. Secound question is whether someone will bale it and take hay as payment. Contrary to what many believe,hay doesn't have to be weed free before someone will buy it. Too many unanswered questions to allow BEST answers to your questions.