First, measure the old balusters and from the bottom of the sill plate (which is slightly under floor level) to the underside of the handrail (Image 1). In this example, the measurement is 33-1/2". Never assume that the measurement is the same all the way around. Be sure to take this measurement at several places.
Mark the measurement onto the new balusters and add 1/2" (for the fitting of the baluster into the round hole) for a total measurement of 34".
To make the measuring and marking for all 200 of the new balusters a little easier, create a jig by clamping a piece of wood onto the back fence of the saw and slide it down to the stopper (Image 2). This will allow you to cut all of the balusters to the same length.
Slide each baluster into the saw and cut (Image 3). After cutting the top, cut about 1/8" off the bottom to help each slip into the sill plate easier. Repeat the cuts until finished.
Place the balusters in an upright position to be painted. To do this, create a support for painting, start by inserting staples about 4 inches apart into a 2x4. Set the stapler so the staples don't drive all the way into the wood. Also, be sure to set the staples far enough apart to give the balusters ample room during painting.
Next, staple into the dowel end of each baluster so that only one side of the staple goes into the wood. This should allow a hook to be created.
Continue this process with the 2x4s until you have stapled hooks on your 2x4s for each baluster.
To create a work frame, use ladders as corners or end supports. Fill the middle horizontally -- and the sides -- with the stapled 2x4s.
Hang the balusters in rows onto the 2x4 frame (Image 1). Make sure none of the balusters touch and that you have access to both sides for even coverage.
Fill the sprayer with the manufacturer's recommended type of paint (in this example, latex is used). Keep in mind that oil-based paint cannot be used with many types of sprayers.
Begin applying an even coat of paint to each side of the balusters and allow to dry thoroughly before installation (Images 2 and 3).
When adding balusters, carefully measure between the existing balusters and make a mark for drilling.
Use a reciprocating saw or hand saw to remove the existing balusters. Cut through the center of each baluster, then remove each section of the baluster by pulling from the top and bottom holes.
Use blue electrical tape (Image 1) to mark your spade bit at the correct depth needed for drilling. Use the spade bit to drill holes in the handrail (Image 2) and the bottom seal plate to set new balusters. Drill the hole slightly deeper than the length of the balusters to allow them to slide in and drop easily into place -- but avoid drilling through the handrail.
Use glue on both ends of the new baluster -- and in the holes -- before setting into place (Image 3).