I've found every method has been tedious, but I've not tried masking fluid.
I use green painters tape from an auto-supply store. You can buy it in very narrow widths that will curve. [And the blue tape is really for latex, not VOC solvent paint.]
Still tedious [for me, anyway] bending that tape around all those curves, then affixing wider tape next to it for the bulk of the mask. So,
I've also just taped a wide strip over the entire lug, and instead of marking, removing and scissoring like @
3alarmer above, I use a very sharp exacto knife and cut while the tape is in place. You'll need to cut just off the edge of the lug, so you can fold it down.
Be prepared to spend some quality time no matter which tape option you choose.
(One of my projects - easier lugs, but more areas)
