Dude you need to spray or you will be out of business quick. or market your business for hand staining and charge accordingly. 13 hours to do a deck? hope you charged them $900! Just buy some disposable drop cloths a bunch of $2 clamps, clamp the drop cloth on the inside deck side, spray at an angle the left corner of the spindle in, work your way from left to right then do the reverse. You will have hit the outside edge twice. go fast, so you are not spraying too much. Then get a new drop cloth tack it to the outside and spray the one side facing in. Get an 8" or 6" inch stain pad and do next to the house, so you don't hit the house with overspray. Once you get the hang of it you should be able to stain/seal a deck in 2.5-3 hours. and why are you sanding the spindles? did you fur them up or use too much pressure. I used to use a scotch brite pad on them when they were still wet and do a quick rub. I sealed 7 decks in one day by myself, using the method I described. I was using Olympic Natural look protector plus by the way, which is the same consistency as ready seal and just as forgiving. For Wolman or Cabot I used an airless sprayer and never had a problem. I made my own sprayer with a 1.6 gpm, 45 psi shur flo. It lasted a year and a half before I needed a new one. The thing made me many thousands of dollars. Once you get the hang of spraying you will never go back.
If anyone asks you to do a two tone solid stain...run! That goes for stripping a solid also...run!
