We currently lubricate linear bearings with grease as recommended, but in very dusty environments it becomes grinding paste.
Is anyone in the same situation and is there a better way to lubricate may be using a dry lubricant.

a semi fluid grease like a #00 or high vis oil like ISO 1500 or so at least when re lube there will be a flushing action.
bruce

macabf;- is there any possibility to inclose those bearings and that way protect them from environment? Have you consider replacing those bearings with greaseless system?

Bruce is absolutely right. here oo grade or o
gr. can be used to keep out dirt conntaminant

If load is not high, You can probably consider anti friction caoting spray as well like Berucoat AF 438 from Bechem.