How big of an area is it? Is it to steep to get equipment on? Do you have access to any if its not? You may want to start a good spraying plan this summer and into the fall to get the grass killed off. Then come next spring you can frost seed some clover, or maybe a clover chicory mix, or something similar. I have done something similar at my place, ive gone from about 2 acres to mow down to about half an acre now, not because it steep just because I hate cutting grass and like to watch the deer. I have been battling the grass regrowing in my plots for the past few years because I didnt get everything killed. Save youself the hassle and do it right the first time.