How do senior bankers use relative P/E in final-round preparation: standard drill with numbers?

A standard drill: acquirer trades at 20x P/E, target is acquired at 15x P/E, all-stock, no synergies. Because acquirer P/E is higher than acquisition P/E, the deal is likely accretive. If the acquirer trades at 12x and buys at 15x, it is likely dilutive. Then layer in synergies, financing mix, tax, and PPA to refine the answer.