I have an outside corner where plaster on one side meets exposed brick on the other. It all used to be plaster but I stripped off the side where it's now brick. The line is pretty straight cause I cut it with a 4.5" diamond blade but i would still like to make the corner fully plaster, i.e. cover the gray 3/4" thick old plaster with finishing to look like the plaster on the right side. IOW, I don't want the inner coat of plaster to be visible.
What I was thinking of doing is take a 2x4 and affix the 4 side along the brick side and the 2 side flush with plaster (hold it in place clamped to an adjacent window recess) and then tuckpoint the hole between the 2x4 and plaster to make a perfectly molded corner.
My question is: What is the best type of compound to do this with? I need something super light and strong so that it keeps adhered and doesn't crumble. I am afraid my plaster mix (2.5 masonry sand to 1 hydrolic plaster lime) might crumble and detach. Is drywall quickset mud a better option? Once I have molded the perfect corner, I plan to put a metal corner bead (using adhesive, not nails)