day 1 due diligence on small SMBs: manual excel vs dedicated tool?

running into the classic small deal dilemma on a couple $2m SMBs. the seller’s bookkeeping is a total disaster—accounts renamed halfway through, personal expenses hidden everywhere, chaotic chart of accounts.

for deep diligence, paying a boutique firm or analyst makes sense later on. but for the initial "should i even write an LOI" phase, i just need a fast way to normalize the trailing 24mo and check for deal-killers (customer concentration, revenue vs bank deposits).

is everyone still doing this line-by-line in spreadsheets for every single lead, or is there a lighter/faster workflow you use just to weed out the bad deals on day 1?