How to populate custom fact table with core facts

Hi,
I am trying to setup a custom/specific checking account table fact as suggested in "The Data WareHouse toolkit", and would like your opinion on best approach
to populate core facts in this custom fact table using SSIS as ETL tool.
Core fact table is obtained almost directly from source and include all customer accounts.
Custom facts are obtained from aggregate transformations on transactions/month and are both CPU/memory intensive. As so we first extract these transactions from source system and then perform aggregate transformations for each checking account. The question arises on when and how to load these along with core facts ?
 
Regards
david

You load them at the same time. What you don't want to do is two passes to load the fact table.

Hi BoxesandLines,
In this case I would ( in SSIS ) repeat the core flow pipeline ( multicast updating and inserting new facts) and then merge with custom facts, or merge before and then repeat flow pipeline with all facts but updating and inserting only relevant facts for each fact table ?

Thanks for your reply
David

That I would not be qualified to answer.

Thank you anyway.
In your experience do you load core fact table and custom fact table at same time? How did you do?