Rental services for purpose of this revenue procedure include: (i) advertising to rent or lease the real estate; (ii) negotiating and executing leases; (iii) verifying information contained in prospective tenant applications; (iv) collection of rent; (v) daily operation, maintenance, and repair of the property; (vi)
management of the real estate; (vii) purchase of materials; and (viii) supervision of employees and independent contractors.
Rental services may be performed by owners or by employees, agents, and/or independent contractors of the owners. The term rental services does not include financial or investment management activities, such as arranging financing; procuring property; studying and reviewing financial statements or reports on operations; planning, managing, or constructing long-term capital improvements; or hours spent traveling to and from the real estate.

You should start documenting the hours spent. For 2018, you can estimate and claim ignorance. The probability is that the IRS isn’t going to audit this for 99.9% of rental property owners. The worst thing that can happen is that you pay back the QBI reduction.