Use Flash to combos and Ignite to anty heal and deal bonus damage. (Always ask your adc to take heal)

Wait for aftershock to use E , taunt and always msg ur adc to go in (aftershock is good to healing after trading)

First build boots after that mythic for slow hydra for damage warmogs for regeneration and axiomic arc for r cooldown. Change trinket when u get supp item wards (when u have 5 items sell support item).

1.Flash + E
2.Flash + E + Q + W
3.R + E + ignite + Q + W

Main reason of shen being a support is his ultimate ability wich is greate for roaming and supporting other lanes. Other reason for shen being a support is his third skill (E) wich taunts enemy and makes them attach you if u combo it with second skill (W) it becomes a stun bcs W blocks auto attacks and E (taunt) makes enemy attack you with auto attacks so they dont do anything. You can also use W just to shield your teammates from far range auto mainly works on adcs like senna and jinx and blocks powered by passive lux attacks. Use your q to slow enemys while runing away and then use ultimate to run away.Shen is a good support and he isnt countered much on botlane only thing he cant survive is an unbalanced champion like pyke.

First runes:
Aftershock - Greate tank rune used by most of tank supports.
Shield bash - Work greate with your passive wich gives you a shield every 10 seconds.
Second wind - Gives more regeneration.
Revitalize - Buffs your passive and gives more shield.
Second runes:
Cheap shot - Gives you more damage after using your E skill.
Ultimate hunter - If u get all 5 stacks u get up to 25% cooldown reduced on your ultimate ability.
Third runes:
Ability haste - gives 8 ability haste and its greate for your ultimate ability.
Armor x 2 - gives you more survivability on lane it really dont really matter in teamfights bcs its just 16 armor.

Plated steelcaps - Just best boots for tanks.
evenshroud - gives you tankyness and slows damage when tounted.
redemprion - gives hp and heals teammates.
Thornmail - gives armor hp and antyheal.
Warmog - Ability haste, hp regen and health mostly for healing passive.
knights vov- gives your teammates more tankyness.
Oracle lens - just a good item helps finding invisible wards.
demonic embrace - gives ap and makes your ultimate more op.

Use your control ward to make safe your junglers red/blue buff. If ur not helping your jungler and enemy botlane is helping they jungler then go and stay in the blue side bush in the river. Ping ur adc to help you and wait in a bust for enemy chempion to go ward bush. When they come by use E and get first blood (its the reason to take ignite).

First u max Q (first skill) for more damage.
Second is E (third skill) for lower cooldowns for taunt and kills.
Third is W (second skill) for more shielding for teammates.
And finally when u can u have to max your ultimate attack (R).

As a shen supp you cant carry the game but you can help carry game with your best teammate. In late game try to follow and help teammate wich carry team use Ultimate R on him shield and tank damage he gets with W skill.

On support its easier to get mor points becouse its support and its easier to get 7 tier bcs its easy to get S+ on support and you dont even have to carry the game.