For exterior brightwork consider "Honey
Teak" (www.signaturefinish.com) a 2 part + 2part catalyzed acrylic-
urethane copolymer system (base + clear overcoat).
Been there done that .... oil, resinated oil, paint over, epoxy
encapsulation then varnish over, multic coat varnish combos of oil
based with urethanr over then clear 'interthane' over that, cetol,
bristol, etc. etc. etc.
I have a 'teakey', have been using Honey Teak and Im in my 8th season
with only a few major spot repairs. Requires a yearly slop coat of
'clear'. Sands with a purple 3M Scotchbrite pad - just 'scuff'
it.

...... but, this stuff can be hand rubbed or powerbuffed to a gloss
that will make a Hinckley turn green with envy (almost).
The manufacturer is direct sales and will 'split' so you only need the
amount you 'need'. Somewhat expensive but when you amortize over all
the years that it stays intact winds up being the cheapest overall
versus the highest gloss that 'lasts'. It goes on initially with a
dark amber hue but quickly fades to an amber (like a multicoat oil-
based varnish), becomes lighter and lighter hued the longer you have
it on ... and you can actually see the grain like a 'real' varnish.

Im into my 8th season and its only now needing major repair (blackened
scarf joints, etc.).
The 'instructions' are somewhat vague ... my recommendation is to
apply at the 'coldest' ambient temperature so that you get good flow-
out and lay it on THICK (I use 3 base coat applications) so you get
the best UV protection of the wood cells beneath. You can put on many
coats in a single day on horizontal surfaces; but, needs the vertical
surface to cure well before successive build-up coats. I powerbuff
instead of hand rubbing after flat sanding to develop the 'glowing
iridescent/shimmering patina' of a 'first rate' varnish job. Can be
easily removed with normal 'paint lifters/strippers'. HT has a sharp
learning curve for application.