hey guys, I have a place I bid on that has a very steep stone drop off because his property sits about 20 feet higher than the neighbors. The problem is it's too steep to walk and weed trim but there are very thick bush like weeds that grow out of the wall. Is there any weed/grass killer you guys would suggest? Does any 'kills-all' come in hard fertilizer form so it would get inbetween the rocks? Thanks let me know!