FWIW ceramic bearings are a waste of time and money. Modifying the hub to use a less viscous lubricant and with less seal drag etc will yield small gains for a small amount of effort. If there are contact seals you can remove them if you intend to ride in dry weather only.
Note that the apparent gains from changing lubricant are always less than you might think; the losses are pretty much invariant with load and most greases have a shear thinning characteristic, i.e. the additional losses (from the lubricant viscosity) don't go pro-rata with speed as you might expect. By all means try this stuff for yourself, but with a built wheel (in a stand) you may see no difference in run-down times between oil and using a small amount of a decent grease.
FWIW the biggest difference you can make with cup and cone hubs is to pay careful attention to the adjustment; the correct adjustment is to have a little free play in the bearings that just disappears as the QR is tightened.
If you have no such free play, once the QR is tight, you will increase the preload on the bearings enormously (up to five or ten times the service load is possible on a front hub) which will increase the bearing drag by a far greater amount than any amount of messing about with bearings and lube would ever save you.
You should ideally set the hub bearings using a proper hub vice, but you can at least test the bearing adjustment is correct by installing a thick washer each side of the hub (as dummy dropouts) and tightening the QR. With a correctly adjusted front wheel (or a rear in VDOs) you can vary the QR pressure so the hub bearings just transition from 'a little free play' to 'no free play' and are therefore operating with minimal preload.
The cone adjustment ideally needs to be accurate to just one or two degrees; if you can manage this you can set the bearings to single-digits of microns, i.e. a better tolerance than that which is likely to be achieved by a cartridge bearing once it is installed.
[NB Because the ball bearings are larger than in a typical cartridge bearing, the coefficient of rolling resistance in service (i.e. under load) is less with a cup and cone hub, which is why both campagnolo and shimano persevere with them in their professional quality equipment.]
cheers
