Varnish work is a thankless job. Unlike a headliner I may install and the customer sees instant "wow", quality varnish work takes time.
I have used the heat gun method, a "DA" sander, and old fashioned hand sanding. The old fashioned hand sanding is the least harmful to the wood and I recomend long strokes with 80 grit.
I also recomend Epifanes varnish and regqrdless of what the can says, I always sand between coats with 220 grit and I always use 3m sandpaper.
Some one mentioned cutting the first coat by50%. This is the formula all the pro brightwork specialist use. Excellent advise there.
The first coat may even look worse than the original varnish. That is why it is a thankless job , until the final coat is applied.
Here are a few hints for those who wish to undertake this project.
1) It is time for the last coat when you hand sand the varnish and the entire piece of wood turns pure powdery white with ZERO grain lines showing. ( this is normally around the 10-12th coat. ( your finished teak will look like it is coated with glass)
2) Keep the brightwork new by sanding with 220 grit, by hand , every spring and fall and applying 1 or 2 coats of the same type varnish. ( again I prefer Epifanes)
3) There is a product called Penetrol. It will make these heavy varnishes flow smooth and all brush marks will dissapear. ( this product also works great with any oil based product such as polyurathane paint, however the light colors such as white may in time show a "tint" due to the penetrol )
4) Another product to use, especially in the winter time is Japan Dryer. This is an accelerator for for a quicker dry time and works great. I have used it with varnish and Brightside poly with very good results.
5) Never use the can for retrieving the varnish. Pour the varnish you will be using into another container. You may be surprised at how much dust and particles can accumulate in the original can. Clean varnish is as important as the preperation and application.
I have seen the "epoxy" used over the raw wood, then coated with varnish, and I am here to tell you........it gives a false sense of security. Varnish, regardless of brand, breaks down because of the elements and even more so due to the UV rays of our sun.
When this varnish breaks down the epoxy will discolor usually dark brown or black. Then you have no choice but to start from scratch all over again, but removing the epoxy is much harder than removing varnish.
Aside from a "Real Lady" , I do not think there is anything more beautiful than properly varnished teak.
Good luck !
I had forgotton one of the most important items. The Brush.
I use a Badger Brush. Hate the foam brushes. Clean the Badger Brush daily with thinner, then wash with soap and water. Get it dry, then wrap in a lint free cloth ot paper towels.
Dip in thinner a few times and shake well before using the next day/time.