What magic system is Hoid using?

[Valhalla]

In Chapter 1 of part 2 of Secret History, when Hoid meets Kelsier, the following happens:

He reached down to the corpse he was using as a boat, then removed something from his pocket. Something that glowed, though Kelsier couldn’t tell if it was something naturally radiant, or just something made of metal. The glow faded as the Drifter administered it to his vessel, then—covering the motion with a cough, as if to hide from Kelsier what he was doing—furtively applied some of the glow to his oar. When he placed the oar back into the mists, it sent the boat scooting closer to the Well.

Sanderson, Brandon. Mistborn: Secret History (Kindle Locations 455-459). Dragonsteel Entertainment, LLC. Kindle Edition. 

What magic system is he using here?

[Yata]

No System, he simply used some distilled Investiture to interact with the mists that compose the Scadrial's CR. Without that he would be unable to push on the mist and made the corpse-boat move.

How he distilled (if he was the one to do that) the Investiture in the first place is unknown, but we could assume it's the same method the Ire's drink was made from

[Quantus]

Short answer is that we dont actually know.  We know he has reached at least the 2nd Heightening of Biochromatic Breath, he has access to Unsealed and Unkeyed Scadrial Medallions, Invested Sand from Taldain, uses a form of Lightweaving that predates the Rosharan Radiants and is from Yolen, and possesses a Lerasium bead he may or may not have used himself (though there were moments that looked like he was downing metals, so...). 

Spoiler

 

There's a reasonable chance that he has bonded a Cryptic and is a Knight Radiant now too

 

If I had to guess from that scene, Id say it was breath Awakening by the way he applied it (having presumably stored the Breath in an object the way Vasher does), but rather than trying to actually use the Awakening I think he just needed to Charge it with Investiture enough to get the oar to interact with the Mist.