We have a low-tech solution that uses 5-gallon bucket lids painted with crosses and then we have 20"x20" thin aluminium targets with reflective tape (like highway signs use). Other times we just paint crosses on the ground with paint, but those are mainly checkshots.
We survey the GCPs and checks with a Trimble R10, using VRS, RTX, or corrected to a base, but we prefer the RTK networks when we are in cell range. We usually tie into several known points for verification, too.