For teak decks I use a mixture of 1/3 Teak Wonder, 1/3 Semco Natural, 1/3 Olympic Deck (carmel). For prep I wash/etch with TSP, then bleach with Oxalic Acid then Clorox to bring the teak to a 'light' color. The 'mix' prevents the 'ugly greys', isnt slippery when wet, seals the seams and bungs, is light in color so it doesnt soak all that much 'heat'. 2-3 coats followed by a coat every 6 mos. is all that it takes; although burying the bow under green water on long passages will lessen the 6 mos. requirement. Teak is expensive nowadays (~$35.00/ bd. ft.) so its probably a good idea to protect it.
For 'bright' I use "Honey Teak" (
Signature Finish and Honey Teak Products - Home) - if properly applied will last upwards to 10-12 years in hot sun, requires a yearly clear 'slop coat'. VERY expensive, has a high learning curve to make it last. Catalyzed 2 part base + 2 part top clear coat - can be applied wet on wet (with some time to allow catalysis) on horizontal surfaces but needs some cure time for vertical surfaces. Mfg. recommends 2 base coats but I apply three THICK coats to insure longevity. Looks like butt ugly Cetol for first month after application but then quickly fades to a clear amber hue very similar to oil based varnish. Probably the closest synthetic coating to varnish ... as its quite 'transparent' (after 30 days cure).
Can be flat sanded and hand-rubbed (or power buffed using 3M perfect-it & 3M finese-it) for the most brilliant, most glossy finish that will equate to a "hinckley type varnish job" ... (handrubbing will develop a glowing irridescent 'patina' of the surface wood cells - just like on 'prime' varnish jobs). Is a urethane/acrylic copolymer; therefore it can be 'powerbuffed'. Must be applied THICK for good service life; if applied 'thin' will quickly fail in UV exposure. Shouldn't be applied if dewpoint is rising and temp. is dropping - greatly retards the catalyizing/cure. Can be applied to hot surfaces but best is applied to COLD (45-50°degF.) so that you get good 'flow-out'. Apply with quality foam brushes or 'soft' artist brushes. Needs to be 'scuffed' with 3M purple pad between cured coats or when applying yearly maintenance coat.
Manufacturer will supply 'splits' - just the amount you need to do the job. Downside is that user must carefully mix the proper percentages of the components (HT, catalyst, thinner). Its expensive but when you amortize over the service life (including the 1-2 year maintenance coats) its probably the most economical overall. HIGH learning curve: but, If done right will make a Hinckley blush with envy and will last up to 10-12 years (with yearly quick 'maintenance' clear coat).