I believe Helium at -400 is frictionless to itself, or to anything passing through it. It would not, however, act as a perfect lubricant. It in fact has a lubrication effect of nearly 0. Instead of acting as a "Go between" for 2 surfaces, it would be extremely good at getting out of the way.
Normally, surfaces viewed at high magnification (or even at the molecular level) are incredibly rough terrain, and it is the massive mountains and deep valleys scraping over each other that create friction.
Oil works when layers of the liquid form a film over the surface of a material. This film fills in the "Valleys" and rides above the "mountains" as well. 2 surfaces covered with oil touch each other, instead of the surfaces of the layers the oil films are attached too. As oil has innately very little friction between itself, and the surfaces are (by hydrodynamic nature) very smooth even at the molecular level, friction is reduced.
A force field would act as a perfect lubricant, as it has no "Surface" for the other material to scrape against.
While this surface is in fact frictionless, that does not mean that there is no resistance to movement across it. That would depend on exactly what the nature of the "Force" is (no star wars jokes please)
An example would be if you took a large chunk of Aluminum and tried to move it quickly through a strong magnetic field. The result would be that the faster you tried to move it, the more resistance you would encounter, even though you never touch anything. In fact, the metal would quickly become to hot to hold onto. (I have experienced this first hand).
In the end:
There is no way to define the true properties "Force Field" until we actually create one
The resistance to motion can not be determined logically
The surface would in fact frictionless,
This should mean that would be a DM determination in each campaign.
Personally, I always liked the idea of it being frictionless (no resistance), so many neat trap opportunities.
