Measure and mark the cardboard forms to length. Set the table saw fence so that it is as far away from the blade as the length of the short end of your cardboard form. Set the height of the blade all the way up. Start the saw and spin the form to cut the form off on the mark.
Set the cut-off end of the form on a sheet of 3/4-inch MDF, and trace it onto the MDF. Retrace this three more times. Use a compass to draw two circles 1-1/2 inches wider than the circles you traced. Cut out all the circles with a band saw.
Apply wood glue to two of the smaller circles. Nail a second small circle on top of each of these with a pin nail gun and 1-1/4 inch nails. Use six nails evenly spaced on each of these pairs of circles. Glue and nail one large circle to each of these stacks, centered to overlap 3/4 of an inch on all sides.
Fit the two stacks of circles into the ends of the tubes and staple them in place, with one 1-inch-wide crown staple from an air stapler every three inches.
Cut strips of 1/8-inch hardboard on the table saw two inches wide. Cut enough strips to length to fit around the column with two inches between each strip. Glue and staple these strips to the cardboard form vertically, spaced two inches apart to create "flutes" around the column.
Glue and wrap one strip around the top and bottom of the column, up against the top and bottom of the column. Staple it in place with one staple every two inches.
Mix one part white glue and two parts latex paint in your choice of colors. White and light gray work well for columns. Brush on a coat of this mixture, coating the entire column.
Tear muslin into strips six inches wide and 12 inches long. Paste them on top of the paint and glue mixture. Brush on a coat of the same mixture on top of the muslin. Cover the entire column with muslin strips. Allow the coat to dry to the touch and coat again.