Keep in mind that there are many opinions regarding the best way to glaze sash.  The following is the opinion of Weston Millwork Company. and the method that we use.  It probably isn't the fastest method, but we are interested in the best quality and longest life.

We recommend that sash are back-bedded with a bead of latex caulk such as DAP (R) Alex (R) Acrylic Latex Caulk.  A small (1/16") bead around the inside edge of the glass rabbet is adequate.  Press the glass in evenly and hold it in place with glazier's points.

The latex caulk is semi-adhesive, so that the glass can easily be removed from the sash in case of breakage.  Failure to back-bed the glass may resuly in glass which eventually becomes loose and rattles in the sash.  Use of high-adhesive caulks such as silicone will result in extreme diffuculty in removing the glass if it is ever necessary.

When the caulk is dry and set (usually few hours under normal conditions), remove any caulk which would interfere with the glazing compound with a putty knife.  Then apply the glazing compound and finish to a neat appearance with a putty knife.  The putty line should be the same width as the glass rabbet (3/16" for standard storm sash). We recommend and use Sarco Multi-Glaze Elastic Glazing Compound manufactured by Sarco Putty Company in Chicago, Illinois.  The Multi-Glaze is a high-quality glazing compound made for glazing wood sash.  We have had much better, longer lasting results with the Sarco glazing compound compared to the common white glazing compound available at any hardware store.  

The Sarco glazing compound can be painted over directly; it does not require a prime coat.  Wait until the putty has skinned over before you paint it.  The time required for skinning over varies according to temperature and other ambient conditions.