Several constructions of optimal bandwidth $(n,k,l)$ MDS codes exist. Letting $r=n-k$ be the number of parities, Ye and Barg constructed $(n,k,r^{n})$ RS codes with asymptotically optimal repair bandwidth; they also constructed optimal bandwidth and optimal update $(n,k,r^{n})$ MDS codes. Wang, Tamo, and Bruck constructed optimal bandwidth $(n, k, r^{n/(r+1)})$ MDS codes. A key idea in these constructions is to expand integers in base $r$. When $r$ is an integral power, we refine this technique to improve the sub-packetization of the two Ye--Barg constructions while achieving asymptotically optimal repair bandwidth. We also reduce the sub-packetization of the Wang--Tamo--Bruck construction while achieving a repair-by-transfer scheme with asymptotically optimal repair bandwidth.