Painting old cement/slate walls

I have just moved into an old farmhouse and am trying to tidy up an old barn to use as a garage. The walls of the barn were covered in green mold most of which I've managed to get rid of with a water bleach solution. I'm now trying to paint over the old limewash walls using a straightforward lime/water mix but it's proving to be virtually impossible because of the depth of the cracks in between the cement and the slate, and even in the slate in some places. Two coats and it's looks like nothings been done. A roller would be even worse I think!

I'm only trying to tidy the place up, not make it to a 'good' standard and I wondered if there was a cheap way to spray it, and if so what I needed to get please? Would there be any use in keeping the lime mix thin and just spraying it over and over?

Thanks in advance for any advice.

Where is the "cement and the slate" !

Is it on the walls ?

If so, then i would use Dulux Trade Stain Block Plus.

Followed by two coats of Vinyl Soft Sheen.

I would do this whilst the weather is warm though.

Thanks for the reply.

It's actually an old slate built building with cement holding it together, so instead of bricks or breeze blocks for example it's slate! Very very rough it is too!

Are the paints that you recomment sprayable because that's my problem getting into all the nooks and crannies!

when i was a young guy we used to apply lime wash with a sterup pump
but if it got in your eyes or cuts it would make a mess of your skin
having seen anybody put these stuff on for years ,also you could get it grit-blasted of it would make the slate look good and you would not have to paint it every again i do alot of jobs like this

If it's a slate building, and that old, I bet it's lime mortar, not cement. It might need repointing but it will be an old-fashioned building method and need advice from someone local familiar with restoration of old buildings.

I wouldn't use a modern paint which may prevent it "breathing"

I used to stay at a climbing hut in Borrowdale like that, IIRC the inside walls had lime plaster on them.

JohnD is rigth bet it is lime mortar but if you blast it off you will love the results