Question regarding sanding after first coat of undercoat

[kilo_4que]

Hi guys, people say you need to sand after undercoating, how much do you actually sand down.

I have also seen instances where once sanded down the wood grain shows through and the surface looks as though its just been chalky stained in white. How does one get such an effect as when i try sanding down even lightly, in some parts it goes to the bare wood at times.

Thanks

p.s. i am using wood primer/undercoat by dulux

 

[Robbie uk]

Dont rub down bare wood until it has had a coat of primer. This will bind the surface together and lift the grain of the wood. A good sanding down will cut this lifted grain back. Then apply an undercoat. when dry sand this with something like 120 grade. Not too hard and try not to go back to bare wood especially on the harris edge. Each time you sand you use a slightly higher grade of sand paper. I use aluminium oxide paper which is green or yellow and comes on a roll. this last longer and wont clog. There will always be dust particles in the air that will find their way onto the painted surface. Dont need to rub too hard to get this smooth.

 

[kilo_4que]

Robbie i used something called wood primer undercoat by dulux which according to some pro posters here is a decent product.

Likewise i have a single coat of the stuff on at the moment. But it isnt easy to rub down without lifting some of it off