This time of year you should allow three weeks and you should be good to paint it just select a nice dry day brush the render off first with a soft brush and then paint away for external walls Santex is a very good option of pain

You should leave between 2-3 weeks before painting depending on temperature and provided all damp patches are gone , remove any lose dust/render and apply a generous coat of weatherproof paint with a roller or brush
Hope this helps

Abbeysure rendering & building services
The render should go a light colour then you can dust of and seal the.render with a good sealer allow to dry then paint

With sand and cement render the plasterers would have add a waterproof solution to the mix
When the mix has set that day the mix would be waterproof and water should not do any damage to the render
If you can leave the render unit spring next year to make sure the render is dry right though
The top skin of the render maybe dry but it may not be dry though to the base coat
If you paint now you will trap any water and the paint may flake off in 6 months
Water will not harm the render hopefully this will help you

Make sure plaster is totally dried out and frost free then brush off any surface dust.
Proceed with application of sealer clear solution for new render and the apply exterior masonry paint preferably oil based for longevity