Home made side dresser

I am going to try to make myself a side dresser this winter. I have an old 24 row band sprayer for the frame. My thought was using double disc openers from an old drill. I plan to pull my 2300 concord cart and run dry urea... any reason the openers from an old drill wouldn't work to get the fertilizer in the ground? Also is there any reason to go with liquid N other than convenience? Because urea is significantly cheaper per actual pound of N.

Home made side dresser