Advice on plastering/painting the main walls of my farmhouse

[Le Scouse]

Hi guys (and gals)

I have millions of questions, but i've decided to prioritise rather than asking questions about things that i'm not going to get around to until the next millenium !!! I would initially really appreciate anybody's expert advice regarding what to do with my  walls.

Basically I have a 19th century farmhouse, with a couple of stone walls and a couple of  thick walls made out of  what has been described to me by one person as agate and by another as cob. It's sandy in colour, chalky with what looks like tiny sandy stones in the mix.. in parts it just seems to be dust and straw. Its quite strong (it's holding up my house!!) but it doesn't appear to be waterproof as the surface turns to a wet clay/plaster consistency when it rains and it absorbs moisture. Internally it always feels damp even in the height of summer.

My question's are

1. Can I plaster over it when it is dry in the summer?

2. Can I emulsion over it (english vinyl matt/silk for example)

3. Or Do I need to use any special french paints (ideas/brands would be helpful)

4. On the outside, can it be rendered over or painted over. If paintable, could I use sandtex or dulux weathershield for example or is there a special type of paint?

I understand that it's a traditional material and the construction allows the walls to breathe, expand and contract etc, its just that the walls are damp and externally need some small patching, and I just need to know how I can seal/decorate internally and what materials can be used externally to protect and repair the wall (repairs in terms of crazing and small potholes)

I can mail pictures to anybody who is willing to offer advice. I'm sure the wall is not unique as this material appears on most farmhouse in the area. Apologies if i haven't identified it or described it accurately

Thanks for reading

Lee