Can I just enter one entry as a remodel for $12K under assets?
Yes. Since you have only one bill for everything including the painting, that pretty much confirms your painting was "a part of" the property improvements. Just enter everything as one item (assuming it's all placed in service on the same date) in the assets/depreciation section, classify it as residential rental real estate, and it gets depreciated over the next 27.5 years.
