Preparing rubble wall for rendering

I want to render an internal basement wall.The neignbours basement lies beyond the wall which is above ground level.My plan is to flatten wall by removing high spots,attach expanded galvanised metal and render.I will complete the process by applying tanking slurry to render finish.I would welcome advice on the following

1.Which is best way to remove high spots-bolster chisel or scutch tool?
2.Should I seal the limewash wall with SBR?
3.Should I add SBR or similar to render mix?

 

Aside from your other questions, I’d use stainless steel mesh not galvo

 

you intend to remove high spots off stone?