I AM PREPING MY BATHROOM WALLS FOR PAINTING, NEAR MY SKYLIGHT AREA IN MY BATHROOM THE TEXTURE IS CRACKING OR CHIPING AWAY AS I SAND, SO DEEP IT IS DOWN TO THE DRYWALL (BROWN AREA OR CARD BOARD OF DRYWALL), SOME AREAS ARE SO SMALL IM NOT SURE TO USE PRIMER ON THEM OR JUST TO PATCH THEM WITH SPACKLING, (THE SIZE OF PINHOLES) OTHER AREAS ARE LARGER WERE I KNOW I HAVE TO PATCH THESE AREAS WITH SPACKLING, SOME PEOPLE SAY USE PRIMER FIRST THEN SPACKLE....PLEASE HELP