I would use powdered "Cullamix" (brand name) tyrolean product, it's made for the job. Just add the correct amount of powder to a measured amount of water, stir/mix it properly, pour it into the tyrolean flicker, (splatter-box), and you're ready to go.... Make sure you stir the mix regularly in the bucket, otherwise it will settle to the bottom,,,, and even with the flicker machine,, stir or shake the contents regularly too, because they settle fairly quickly as well ........ I've never used a home made sand and cement mix to tyrolean finish a wall, although others might have. Cullamix, in a variety of colours should be readily available from your local builders merchant. Using "it" will take all the guesswork out of trying to make your own, and as I said,, just add water, stir regularly, mask/polythene/cover everything, glass, windows, doors, frames, sills, etc (very important 'cos it's messy) ,,,,,, don't overload each coat, build it up gradually, choose a good dry day, and Bob's your uncle.
Also,, you DON'T use PVA before you apply the Cullamix, there's no need to use PVA at all when doing tyrolean ,,,,,, plus, it is also important that the rendered surface/s is "bone dry". If you tyrolean onto a wet,, damp,, or a PVA/sealed rendered surface, it wont work,,,, you will not be able to build up the texture. You need some suction for it to work..... It might seem like an easy job to do, just turn the machine handle, and flick it on the wall, but if you have never done it before, be wary,,,, 'cos there's a lot more to it than that, as i'm sure you'll know.
Roughcaster.
