its really sticky it sets up slower than multi and once its set its absolutaly rock hard so if you dnt get it right your chances of sanding it down are very low, but its the right gear to use if you know what your doin it trowels up nicley (to the desired effect your looking for), but just make sure you get it right.
also if your doin the front of the fireplace and the cheeks (internals) dnt use beads, im sure you know why:RpS_wink:
If it's an old house with many years of coal/coke/wood fires the brickwork is likely to be contaminated due to the products of combustion depositing salts in the brickwork. If the rendering is a weak mix without salts inhibitor/water proofer salts may migrate to surface of render and in turn migrate to surface of lime. If its new house and fireplace has not been used no problem.