blisters

Blistering is usually an adhesion problem.  Adhesion of the plated deposit to the base material is related to inferior pretreatment 99% of the time.  The part must be 100% free of water breaks and must be activated completely.  Please describe your pretreatment process and we can try to identify any obvious problems.

By the very nature of electroplating, you will have less thickness in recesses and interiors of parts.  To counter this, you need to force the electricity to move where you want it to move.  Most people doing alkaline non-cyn zinc use auxiliary anodes to increase thickness in problematic areas.