i'm going to be different and say round-up first after brush-hogging or mowing it. The reason is because in the spring after mowing it all the weeds are putting all there energy into growing again and then hit with round-up and you are sure to get a good kill. We had 14 acres last year that was in CRP grass and we decided to put a wheat crop in it and mowed then sprayed. The thing is with that many weeds it is going to be difficult to till or plow. Spraying and killing first will cause the weeds roots to die and let loose of the soil somewhat making it easier to till. After that once you plant I wouldn't worry too much about secondary weeds coming up your well fertilized forage will crowd most out. Also if planting clovers alot of times people overplant. If you have an acre or less 5 to 8 pound on the whole thing is plenty. Otherwise it robs itself of nutrition. LOL