I used to dissemble FWs, grease and oil but after several came apart and spewed bearings on the road I went to just oil as base2 suggests. And you know what? With my riding, the oiled FWs outlast the cogs easily and since FW cogs are about as easy to find as the hen's teeth at the farmers market, I call that good enough. I follow the old "rule" - oil from the outside; ie the dropout side until you see oil on the inside (between FW and hub if mounted). That should flush any dirt thrown up by the wheel out.

(And a minor editorial point - if you are wearing out oiled FW bearings, may I suggest maybe you should pedal more. Those bearings are only being used as you coast. My favorite bikes don't even have them. )