The tenth coat went down two days ago and it's looking pretty good. It
was a big job however. About 230 linear feet of hand rails and toe
rails plus about 60 square feet of teak overlay on the transom. That's
over half a mile of sanding and varnishing by the tenth coat. Hopfully
it will be good to go for awhile because it is a PITA project. We're
having fitted covers made for the whole works so that should help to
protect the varnish from UV damage when the boat is sitting at the
dock here in the hot Florida sun.

Some lessons learned:

It is really important to heavily thin the first two coats (about
50%). That helps the varnish sink into the surface of the teak which
improves adhesion and also brings out the rich reddish brown color of
the wood.

Use the best possible varnish. We like Epifanes Wood Finish Gloss.
It is expensive but it lays down well and looks good. Even more
importantly, you can put down new coats without sanding if you re-coat
within 72 hours and the varnish has not been rained on. That is a
really big labor saver even though 4 coats is about the max before it
needs a sanding to smooth things down.

Foam brushes rule. I was able to get a box of 48 from Amazon at near
wholesale prices. Get the good ones with the wooden handle. The
varnish brushed out fine with no lap or brush marks, and at the end of
the day you just throw it out which saves a lot of time, energy and
mineral spitits.

For masking tape I highly recommend the green "Frog Tape". I left it
on for the duration of the job, over 4 weeks, and it came up easily
even though it had been wet numerous times and baked in the sun.

Get a really good sander. I like the Bosch 5 inch circular random
orbit model. It is almost totally vibration free, reasonably quiet,
and has excellent dust collection.

Use a heat gun and scraper for removing the old varnish. I've tried
just about everything, and on balance that is the best way. You need
a variety of scrapers to conform to odd shapes but for straight line
surfaces, the large carbide tipped scrapers with the rubber covered
handle seem to work the best. Think about wearing leather gloves to
prevent burns.