Here are the pictures for the drip tube I built.  I got the clear plastic tubing from the Home Depot.  They don’t sell it at the local store anymore, but you may find it at another store.  It was originally sold as dust collector ductwork in their power tool section.  It is 2” OD and 1/16” thick walled tube.  The coupler was an accessory available in the display with the tubing.  McMaster-Carr or Grainger sells the stuff in a couple of different types of plastics and I believe they have it in 6’ lengths so a coupler wouldn’t be needed.  I got everything else from the Home Depot to make the fittings at the bottom and used PVC glued to put it all together.  I just took the tube into the plumbing aisle and messed around with the pieces until I got the parts to fit together the way I wanted.  I tried to leave as many parts as I could that would thread together instead of glued to facilitate clean up (which takes a while after use).  The valve is a 3/4” right angle shutoff supply valve used a lot for toilet or sink installations.  The stand is made from whatever I had left lying around in my shop, as you can probably see.  But it works.

I predetermine the depth of the varnish by holding the section up to the tube and mark the height with tape.  Then I fill the tube (always double-check to make sure the valve is closed at the bottom before you fill - not that I ever didn’t do that, but it’s just amazing how fast varnish flows out of a wide-open valve...) using a funnel and pouring the varnish slowly down along the side of the tube to minimize any air bubbles that may form.  It takes about 2 1/2 quarts to fill.  I then let the whole thing rest for a few minutes to let air bubbles rise to the top if there are any.  It’s never really been much of a problem for me.

I varnish both tips at the same time.  I tie them, using nylon wrapping thread, to the cross pieces with the guides parallel to the spoke used to center the sections in the tube and line them up evenly.  I tie a thread to the rod handle or the cross piece attached to ferrules on the tip section (with the tip tops going down into the varnish) to the makeshift spool made from a 1/4” dowel and two cork rings.  This allows you to lower the sections from the spool into the varnish to exactly the height you want.  I keep the section at the height I want by pressing the cork rings together to cause a friction fit to the plastic tube (I filed 2 slots in the top of the tube for the spool to rest in).  I back it up with tape to hold it all in place.  This is one setup  that might be improved on.  I wouldn’t want the whole section  to unspool and drop into the varnish, handle, reel seat and all...that has not happened yet.

An empty quart can for the varnish sits below the valve to fill as the varnish drains from the tube.  I use a clock to time the minutes and use strips of masking tape to mark the height of the fluid as each minute goes by.  I can then measure the inches per minute as the fluid drains.

I like to control of the valve.  You can drain more slowly, around the guides if you want, and stopping the flow is precise at the bottom of the wraps or wherever you need to.

For butt sections, mask the handle with tape.  The plug, which I make specific to each ferrule size, is wrapped with Teflon pipe tape for a better seal and with spokes (made from bamboo skewers, of course) keeps the section centered in the tube, keeps varnish out of the female ferrule and prevents the section from touching the sides as it is drawn out of the tube.  This is the most precarious point of the whole operation.

Drain the tube completely (close the valve).  Raise the section to the top of the tube with the spool so that you can get a hold on the piece.  I then tilt or lean the whole setup over so that I can carefully draw the section out without having it scrap along the side of the tube.  I can do it without help for a 9’ rod, others may want someone to hold the tube while they pull the section from the tube.  You would definitely need to set up a system for sections longer than maybe 60” (some kind of stand to lean the tube on while the section is drawn out.)  A chair back maybe?

I hang the sections from a hook and clean the varnish from the guides with a Q-Tip and mineral spirits, and then put them in the dryer.  Be careful how much you soak the Q-Tip.  Too much thinner and it will run off the guide and onto the rod (a very bad thing to happen at this point) so squeeze most of the thinner from the Q-Tip (a tip from Bill at Corens).  Hang the tips together to dry and remove them from the cross pieces after 24 hours.  I pull the plug from the female ferrule before I hang the butt section.

I clean the whole rig afterwards with mineral spirits and lots of paper towels.  I fashioned a metal rod from 1/8” stock to push the soaked towel through the plastic tube.  The rest of the pieces I can immerse in a plastic tub and wipe by hand.  I also always take the valve completely apart and do the same cleanup on it.

I hope that this gets you going with a drip tube.  It works well for me and I like the fact that the whole thing is portable.  I can move it out of the way in my small garage and can varnish inside the house if it is too cold outside.  I would be hesitant to try and use a heat tape to warm the varnish.  I don’t want to melt a column of finish onto the floor, although maybe a thicker plastic would work.