If you want to dry hop but want to minimise beer exposure to oxygen, you can do so with the Pressure Transfer Kit.
You can use the Pressure Transfer Kit to supply CO2 to the top of the fermenter to dump yeast matter by attaching the CO2 to the sample outlet of the dual valve and bubble CO2 through the beer while adding the hops at the top of the fermenter. After the yeast dump, there will be positive CO2 pressure in the fermenter. You can then remove the pressure transfer and add the hops through the tri clamp and very little oxygen will get in through the top.
You need active positive pressure from either fermentation or by adding 1psi of CO2 to prevent oxidation and to provide a blanket of CO2 as protection from falling debris.