I myself have a century home and with it still have a few windows, that I just haven't got around to replacing ,that require glazing. I find that when I do them its always best to have lots of time an patients. Its also prudent to have new glass on hand to replace the one that inevitably breaks .doing 3 sides is also a good idea i find leaving the bottom strip of old glaze in place till the other 3 sides are puttied in makes the job faster and your less apt to drop glass. I'm not sure where your located but here in Canada I like to use Dap Latex Window Glazing. I use a caulking gun now instead of the putty knife approach. I tape the window off and that way it makes a neater job. I usually give it a day to cure then go back and do the last side the next day. Just be carefull when removing the old putty and clean the surface the best you can before applying the new putty. Hope this helps and good luck with your windows