Deal expenses as tax deductions

Appreciate any guidance/best practices on maximizing treatment of (particularly pre-closing) deal expenses as tax deductible. I'm a solo searcher. I read somewhere that it is best to ask legal, QoE, etc. to invoice post-closing, I believe to address "“active trade or business” issues. Any other ways to solve for this - e.g., would it help if I formed my acquisition entity? Opened a bank account? Also open to any accountant recommendations. Thanks!