Why do both spraying and rolling sometimes produce a mottled "orange peel" effect?
When spraying, insufficient thinning can create this "dimple" effect on a paint coating. The same is true when using a roller, or it could be the wrong type of roller for the product used. This is normal for such methods of application. To minimise roller mottle, use the shortest pile roller suitable for the finish In any case, to correct the fault rub down with wet & dry abrasion, using water or a suitable solvent, then rinse down and allow to dry thoroughly prior to applying a new paint coating.
What causes "blooming" and how can I avoid it?
This greyish, milky-coloured "haze" on the surface of the paint film is usually caused by moisture attack during drying particularly when painting too late in the day out of season. Thoroughly clean down the surface to remove all dirt, grease and surface contaminants, then rub down with a suitable abrasive and dust off prior to re-applying paint.
I've missed a few small areas when applying a coat of paint. Can I just touch them in?
Unfortunately, no. You'll need to thoroughly clean down the surfaces to remove all dirt, grease and surface contaminants. Then rub down with a suitable abrasive and dust off before applying a new coat of paint to the affected area