Painting internal wooded doors

Give a sanding down, clean the dust. If you use oil base undercoat then you have to use oil based gloss, if you use water base undercoat then use water base gloss

Did you put an oil based undercoat and now using a water based gloss? Did you use any detergent to clean between coats? Would recommend sanding doors down, apply a coat of bin primer sealer and re do doors.

Give it all a good rub down & dust off then use oil based undercoat, de nib afterwards once fully dried with some high grade fine sand-paper, dust again then finish off with a coat of oil based gloss.

I have done this type of job several times and I have found the best way forward is first prepare by rubbing down with fine sandpaper,then you apply zinnser stain block which is in the red can and is meths based this will completely stabilise the surface for painting and ensure that the colour you apply will adhere to the doors and not peel off at a later date .Then apply an oil based undercoat ,then apply the finish

Wait for the door to completely dry then scrape away the blisters.give the whole door a complete rub down as they are new doors 120grit should be course enough.apply an oil based undercoat wait to dry sand down with a 240grit sand paper dust of then apply your oil based top coat you will have perfect smooth finished doors. If you are using water based undercoat and top coat it will be the exact same process.