Should you use tact-based coat before using clear?
Yes, for the most part. However, there are always exceptions. For instance, if you spray a fine mist as your last coat of base (seen with some waterborne paints in automotive refinish), tacking it could remove it. If you are spraying basecoat, you want to tack off between that with a high-quality sticky cloth with less fibers. This will remove overspray, dry spray and any other potential contaminants.