so..where does the grease go that is supposedly reaching the rear bearing? Out the seal I suppose!
Why not do it right the first time and hand pack?
A zillion trouble free miles on the super lube spindles without issue here... even with 10" wheels run at X-way speeds.
I was a service manager at a large RV dealer when Dexter first introduced this system (late 70's, early '80's I think). They sent a factory representative up to our place in the Detroit Metro area to introduce it to us and answer all the typical questions. The guy did a great job and I've been a believer in the system since then.
To answer the first question, the grease travels from the zerk fitting, through the center of the spindle, and exits through a hole located between the inside seal and the inside bearing. It fills that cavity (assuming the seal is still there), then continues through the inside bearing where it's deposited in the area between the inner and outer bearings. When that space fills, grease is then forced out through the outer bearing where you can see it.
The directions do call for the wheel to be turned slowly through this process, so the grease is distributed evenly as the grease flows through each bearing. While not impossible to blow out the back seal, I'm assuming the use of a hand grease gun has much less chance of doing that. I've never managed to do that, but if there is an issue, it's easily seen by the fact the inside of that wheel and tire will be covered in grease.
To answer the second question, because it's not necessary. It's much easier to use the process designed and endorsed by the axle manf. That said, I believe a good maintenance plan WILL have you removing, cleaning and inspecting the bearings on occasion. -Al