Rendering chimney stack

[Dee]

One of the stacks built in commons has blown the paint after 15years. I did prep the rest of the house but not the stack hence the mess it's in now.

Looks like the surface of the bricks have truly blown off. I'm not going to the expense of rebuilding it do I want to render it.

I'll be hiring a boom lift for the reach but I need to know what mix to use and basically how to render a stack!