hope this is not too late for you:

sealer - don't seal with a latex material unless you have the outside of the house done already in synthetic materials.

a sloppy mix of white cement with a bit of acrylic paint to bind it
( bondcrete is better....like the white tube glue material. mix it
2 parts gunk to 2 parts water and add 1 quart to 2 gallons of
sloppy cement mix) also add some mica if you can get it.

even better would be the sloopy white cement mixed with a couple of scoops of lime putty and some mica dust.
dunno if you can manage that.

limewash : you want to get something with a little bit of synthetic
in it (5-8%) so you can tint a strong eggplant colour in the material.

depends where you live. if usa go for italian materials.

methods: a large limwash brush is used. just wack it on,covering
the surface in a grid like manner work down the wall & gradually along. only cut in ( with a smaller brush) as you come to an edge.

you have to keep a "wet edge"
don't be too disturded by the first coat because the second coat
will make it look much better.

maybe email me
metameme@iinet.net.au
easier to find out all the things you don't know.

sounds like you might have some help from a painter....try and find someone who can use a big brush.