I try & paint like the prototype, in this case:
A) assemble hull & upper hull, then assemble turret, wheels & track separately, giving a set of sub-assemblies.
B) Paint the sub-assemblies, including the front & rear of add-on armor, esp. if the armor has a differing colour, EEAK on AAVP's comes to mind here.
C) Tiny bits of mask/elmers' glue to mask the attachment points on the hull/turret & armor will help everything to stick during final assembly.
D) Fit (& fettle to fit) the add-on armour, etc, to the pre-painted hull & turret.
Amend order of A to D to suit your needs, hope that makes sense.