Yes, it's hard to reach those several hundred balls on the underside with your soldering iron.

However, the method I mentioned for soldering PQFP/TQFP packages, as well as j-lead PLCC's and leaded SMT packages in general, works very well, even without a mask. The solder wick soaks up the stray solder, yet leaves the portion that's between the contacts and the PCB in place. All that's required is a little bit of liquid flux, which is easily washed away with a bit of isopropyl alcohol followed by a bit of dish-detergent and a toothbrush together with some hot water.

RE