Honestly, if you're not good with green stuff then I would just leave them as is and paint them in DW colours.
Most of the iconography is interchangeable, like the wings and swords. The blood drops aren't really that prevalent.
If you're dead set on it I'd say using a bit of GS to make a hood on any bareheaded angels (I think there's only 2 or so) and cutting off the blood drops and gluing swords over top would be the easiest.
That's pretty much it, but I think just painting them in bone and white will make people think "Wow, cool Deathwing Terminators"
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