Getting beads and body lines dialed in with body work is almost always a pretty big challenge. It is difficult to keep the shape constant, they are difficult to block sand, they are difficult to spread filler on, they are difficult to block sand up to, etc.
There is no magic answer for them, but there is a way to make it much easier doing body work on beads. It can often save a lot of head ache if you are able to spread the filler on in the correct shape, instead of sanding it to the correct shape. This is the concept used to get beads and body lines really nice and dialed in.
These areas should be basically the last thing to be body worked, since the body work on the surfaces all around the line determine the final shape of the bead. Once the rest of the body work is done, I like to use a thin piece of plastic, and sand it to the exact shape you want the bead to be. This might take 15-20 minutes, but it saves much more time than that, and makes the results better.
Once your piece of plastic is the right shape, and fits the body very nicely, spread the filler on the bead. It works well to be sure there is excess filler, that way to can be squeegeed in and not have any air pockets in it. With the filler spread on the bead, just take the plastic spreader you made, and slowly drag it through to body filler while it is still wet. This might take two passes. Then just let the filler dry and block sand it with 80 grit.
Depending how much body work is required, there might need to be a second spread over the bead after it has been sanded.