VPPs disaggregate frequency regulation signals from the grid to DERs, addressing supply-demand imbalances. However, complex disaggregation of power adjustments can lead to delays, reducing VPP performance. To tackle this, we propose a disaggregation operation strategy that prioritizes low-cost DER while accounting for temporal coupling. To reduce online computational overhead, we also introduce a fast disaggregation algorithm that avoids reliance on optimization solvers, ensuring millisecond-level computation times, reducing adverse effects of cyber-physical coupling issues for VPPs. Case studies with thermostatically controlled loads and industrial processes demonstrate reduced costs and increased profits for VPPs using our strategy. This approach efficiently exploits demand-side flexibility and ensures reliable, real-time grid regulation.