Correct way to paint front door

[AMCLS1]

So I had a new front door put on the house and I'm painting it myself.

I was advised by our painter and decorator to prime the wood, then two coats of undercoat and finally gloss. I think he said two coats of gloss.

I've used zinsser primer 123 and then I've got a dark grey leyland undercoat, I've not bought the black gloss yet as I'm probably going to work from home on Monday and get up 6am give it a coat of gloss and then leave the door open all day so it can dry properly (I will completely tape up the opening and have the door open to protect from any elements)

What grade of sandpaper should I use to rub down between the primer and the two undercoats?

Also would you give it two coats of black gloss?

 

[Robbie uk]

I would prime the door, sand down thoroughly. Dust off, coat of dark grey undercoat. Sand down with p80, dust off, second coat of undercoat. sand off p120
1st coat of gloss. slightly thinned as its cooler now. Don't gloss it at 6am, its too damp then. This time of year you can only really gloss from about 10/11 am till about 2pm as the dew is falling then. when dry I would use wet and dry with water to cut back the gloss and apply a thinned second gloss. This should give a nice smooth finish. There is no need to use Zinsser unless its a hardwood door, and then I would use an aluminium primer first.

 

[AMCLS1]

I would prime the door, sand down thoroughly. Dust off, coat of dark grey undercoat. Sand down with p80, dust off, second coat of undercoat. sand off p120
1st coat of gloss. slightly thinned as its cooler now. Don't gloss it at 6am, its too damp then. This time of year you can only really gloss from about 10/11 am till about 2pm as the dew is falling then. when dry I would use wet and dry with water to cut back the gloss and apply a thinned second gloss. This should give a nice smooth finish. There is no need to use Zinsser unless its a hardwood door, and then I would use an aluminium primer first.

Thanks for your response. It's a hardwood door and my joiner gave it two good coats of oil but I can't see that it is aluminium either way I'd given it a coat of the zinsser before I posted so I'll sand down and then give it a coat and sand again and re-coat.

Thanks for the advice on starting the gloss later and the wet and dry between the thinner coats.

 

[Robbie uk]

Aluminium primer is used as a first coat on new hardwood doors or windows prior to painting with oil based paints.
When the door is nearly dry you can rub the edge with washing up liquid to stop it sticking to the casing.