Determining Assumed Liabilities or Debt, to calculate deal comp EV or TV

Two questions:

(1) Often times for transactions involving private/smaller targets, or unclosed transactions, transaction information is limited, and particularly information regarding the assumption of debt and liabilities. Some financial (deal) database vendors and providers, simply merely apply their own rule in calculating the EV or TV, when assumption of debt information is not available or disclosed.

In calculating the EV or TV, to prepare transaction comps, what do you in these cases?

(2) Also a related question: in preparing transaction comps, do you retrieve EV / TV / purchase price information primarily from news releases and databases (for less formal work, such as portraying trends in a pitch book), and merger related filings (for more formal work such as live transactions and fairness opinions)? Note merger related filings are available only for companies with public securities, and many times, merger related filings disclose very limited information (ie may not show pro forma financials, transaction multiples, or transaction values).

Thank you