Hmmmmm, if you don't even know the correct mix, how do you intend to put it on the wall without devaluing your house by thousands of pounds?
Rendering is a time learnt skill, you can't learn it on a forum.
There are two coats to a render btw, one has to be moisture resistant. There are stainless beads to consider as a bell drip and over window heads.
There is just so much to know, only spending time with an experienced guy will point you in the right direction. I have been a builder for 30 years and NO WAY would I render ANYTHING. I get a guy in. He can render the outside of a large extension in a couple of days so why do it yourself?
Not trying to be a smart-ass here, but it's
much more difficult than it looks.
I'm sure someone will be along in a while to tell you exactly how to do it but 'on your head be it'....... (and it probably will be)