Master Primavera P6 Planner for Cost Reconciliation

Primavera P6 Cost Loading & Reconciliation – Master Schedule (Heritage Projects)
I'm a junior planner working on a design project, and I'm looking for an experienced Primavera P6 planner to help me finalize and reconcile the cost loading on an existing schedule. I've built and structured the schedule myself and done most of the cost loading, but I've hit a reconciliation variance I'd like an expert to resolve cleanly. I'm comfortable in P6 and Excel — I just want this done correctly and to learn from how it's traced and fixed.
The specific problem:
I have the project cost distributed across several subconsultants in an Excel workbook (separate weighted tabs per subconsultant, broken down per palace and deliverable). I need this cost loaded into the corresponding P6 activities as quickly and accurately as possible — ideally using an efficient import/mapping method rather than manual entry activity by activity.
Scope of work:
1. Activity ID coding
2. Map my Excel cost-distribution to the match P6 activities (by WBS / activity ID).
3. Load the costs into P6 (resource or expense loading, whichever is most appropriate — open to your recommendation) using the quickest reliable method.
4. Confirm the loaded P6 total reconciles exactly to my Excel grand total.
5. Give me a short note on the method used (e.g. Excel import, global change, or direct loading), so I can repeat it myself next time.