Dan, I attempted that same situation last year. (DO NOT GO THIS ROUTE) What I did was tilled in spring before green up when weeds were yellow and brittle. I found that after tilling I had nothing but a dirt and weed fluff mixture so I ended up raking and raking until I removed all of the incorporated weeds and grass. I took a soil sample and had it tested and ignored the 2 tons of lime suggested and planted a clover mix. The weather then turned hot and dry and the weeds grew like mad and the clover barely broke the surface.
What I would do is wait for green up and spray round-up. Wait another couple weeks and go back in and round-up any areas you missed give it another couple of weeks and mow and rake out all dead weeds and grasses. Then work your soil and prep the seed bed. Weeds and grasses will still probably grow in your plot but there will alot fewer. I think it is crucial to both get control of weeds before planting and follow your suggestions from soil tests.
I did spray round-up again mid summer and planned to retill the plot and do a fall planting. The round-up killed all my weeds of but never harmed what little clover that was growing so I left it for the year and deer used it still. Best of luck, it’s alot of trial and error to get it right. I can tell you on crp it may take a couple years to get a good seed bed unless you have a bottom plow and turn the soil.