Getting the outer joint off can be a three handed affair. I have always used a pair of spreader pliers and an air hammer to drive the joint off with. First things first is to have the axle clamped horizontally in a vice, access the spot where the circlip is, make sure that the clip is free to rotate in there. If it is not then you need to drive the joint in the direction necessary to free it up. When you remove the axle from the car you usually end up driving the outer joint inwards and binding that clip so you need to drive the outer joint back out just a hair to free the clip. However since you have been banging on it with a brass drift you will probably need to tap on the end of the joint (where the big ass nut goes) just enough to drive it back in a free up the clip. Now with the clip free get in there with a pair of spreader pliers and get it spread real far and do one of two things, take an air hammer with a flat faced bit in it and drive the inner knuckle off of the shaft or have someone else take the big ass hammer and brass drift and give it a good whack to get it started. Either way the important things are: have the clip loose so that when you spread it it spreads ALL the way open and the intial hit, when you give it that first hit make it a real good square hit so that the inner knuckle on the outer joint pops past the groove on the shaft and the clip remains expanded. Going back together is the same thing only in reverse. Make sure that the clip is free floating when you are done. I have had a few axles that I actually put on the press to put back together. I probably could have persuaded them back together with the BFH but having a whole shop at my disposal I choose not to.

Good luck,
Mark