Grease is fine in faster-running bearings where a bit of warmth helps it flow but in slow-moving bearings it just ends up drying and clogging. I use whatever is in the oil can - usually engine oil - as the loadings here are very low. You almost need the oil to prevent corrosion rather than lubricate as the motion is more rolling than sliding. Chain saw oil and slideway oil are both fairly sticky so they stay where they are put - not sure if this helps or not here!