One thing I know I'm not good at is taking a bike with crappy components and making them work like good ones. I have a bike, from my daughter's friend, in my house right now where the rear brakes don't stop. Everything about the setup is crappy, old flexy shifters, suicide levers, old cables, flexy calipers, old pads and steel rims. I can bottom out the rear lever even though the calipers are adjusted close to the rim. My advice is to replace the whole setup but that would cost more than the bike is worth.
And the funny thing is my daughter also just started using my wife's old Cannondale Crit, and while the brakes work I found them squishy, plus the lever/hoods were uncomfortable. New pads, cables and hoods would have helped but I decided to go all out and replace everything including the calipers with dual pivot Centaur and Tektro road levers. When I showed her cross levers for the tops she liked that idea too. She never used a road bike before. She also would like shifters in a better place but that's a whole bigger job, although maybe stem shifters would work ok on the old 6 speed.