brushed on rendering?

as you may have seen in another post I have got a workshop (single skin conc. block) that is leaking.

It seems that painting it will help, but before I do that I'd like to do something to smooth it out a little as currently the blocks are very rough and it's probably going to be a right cow of a job to paint.....


Now, I'm not a builder (that will probably become very obvious) so I'm looking for the right terminology here, but in the house place I had, the interior brick wall in the shed had been coated with what looked like a brushed on render? this would be ideal for filling in all the bigger pores and holes in the blocks to make painting easier, and maybe a good opportunity the get some kind of waterproofing agent in there while I'm at it...

sand/cement + brush marks = brushed on render?

How the hell would you go about trying to brush muck onto a wall?

Any help here much appreciated.

Jelly - stuff we used to use for tidying-up outbuilding walls was called Snowcem (we haven't used it in a long time so I don't know if it's still available). We got it in 40KG drums - it was a powder which needed to be mixed with water then applied with a wall brush. It was very good stuff. Perhaps you could google it to see if it's still available. The reason we tend not to use it is that we now favour rendering.

I'm sure others here will suggest alternatives.

Alternatively the wall may have been bag rubbed.