I also have a speed 10 lathe and have often wondered if I am putting the right quantity of grease in the roller bearings. I pump grease in until it can be seen emerging from the bearing (as per instructions as has been stated ) which means the bearings are full and this is probably too much grease. When the lathe is run ,the bearings eject some of this grease, making the mess described by a previous poster. I can only assume this results in the correct quantity of grease remaining in the bearings.
I have done this for about 25 years and the bearings still seem fine ,so I will continue doing it this way. After greasing the bearings I run the lathe at slow speed for a while to allow the grease to settle down then speed up the lathe to expel the last of the surplus grease.
Doug