We make our bulk liquid blends with some dry ingredients (& some liquid) by holding them in heat. This prevents fallout of (especially) potash. If all you're adding is urea in a soluble small prill or flake form, heat won't be needed. I doubt you'd need more than .33# of additional N to get where you'd want to be. Slowly add soluble Urea to the tank while mixing with the agitiation going. Too large a prill will require that you make a slurry in a pail before dumping it in the tank. You should have your fillwell strainer basket in place to catch undisolved prills. Adding water over the prills will continue to disolve prills without clogging pickup lines.