Before sandblasting or wire brushing, I remove all the Zerk fittings from the piece. In their place I screw in 1/4-28 bolts.

These bolts serve several purposes. They plug the hole keeping paint and debris out and they gives me a handle to hold on to while cleaning or painting. These bolts are also reusable but they do get awfully red after awhile. So dump them in your degreaser every so often.
Ok, so the 1/4-28 bolts were pretty obvious. But here is something that may not be so obvious. On the steering gear arm, there is one Zerk fitting that feeds both tie rods. If you look closely you can see a small hole in each tie rod depression that is open to the hole for the Zerk fitting. The hole is small enough that you really do not want to paint to get into the opening. A possible answer is to use toothpicks shoved into these holes.
But it would be nice if you could keep the tie rod socket clean as well. You have already cleaned the sockets out, so why paint them? You'll only have to clean them again. Here is where you get to use Magic Masking Stuff...

The sockets are covered and this means the grease port is also covered. Once the item is painted, the Magic Masking Stuff (MMS) can be removed. Here is the same steering gear arm after the MMS is removed.

Pretty neat! A 1/4-28 bolt and a little MMS and you have avoided having to clean out the sockets, the Zerk fitting hole, and the grease ports to the tie rod sockets.
At this point you are probably looking for a source of MMS. I suspect that Toy R Us or HobbyLobby or Micheal's all have MMS on the shelves. But they call it Plasticine or Modeling Clay. I suppose that Play-Doh would work as well, but it tends to get dry after awhile.
If you get a little carried away applying MMS, not to worry. It is soluble in just about any solvent except water, this includes, oil, gasoline, paint thinner, acetone, or whatever.
You now have some new tools for those difficult masking jobs. Go for it.
Rick (Field Expedient Spoken Here) Dulas