The Data Behind The Deal

Pretty curious as to how analysts/associates go about building a financial model for a deal: where data is sourced, where specific adjustments are necessary, to what degree specific calculations are made for variables (Beta, WACC, etc.), or if they are pulled from a data aggregator, where the model is warehoused after a deal, how accessing data archives works... etc. I'm well familiar with Bloomberg, FactSet and the like, but what other useful tools to collect information exist? In the end, I'm assuming that all of this gathered data is compiled through Excel -- any alternatives in the model-building phase software-wise? I'm expecting these processes vary substantially by a deal's nature too... Please excuse my naivety as I don't come from a business/finance background, but any insight to this process would be greatly appreciated, cheers!