" It will melt the new clear into the old clear."
Sorry but that is an old wives tale and salesman's blather. Once clear-coat is cured it is inert, it can NOT be re-melted with solvent. NO blender can remelt the overspray into the original clear-coat, your fresh paint only lays on top of it.
Back-in-the-day you could do that with lacquer and actually remelt the blend into it BUT no factory has used lacquer in years.