Nanopore-based resistive-pulse recordings represent a promising approach for single-molecule biophysics with applications ranging from rapid DNA and RNA sequencing to "fingerprinting" proteins. Based on advances in fabrication methods, solid-state nanopores are increasingly providing an alternative to proteinaceous nanopores from living organisms; their widespread adoption is, however, slowed by nonspecific interactions between biomolecules and pore walls, which can cause artifacts and pore clogging. Although efforts to minimize these interactions by tailoring surface chemistry using various physisorbed or chemisorbed coatings have made progress, a straightforward, robust, and effective coating method is needed to improve the robustness of nanopore recordings. Here, covalently attached nanopore surface coatings are prepared from three different polymers using a straightforward "dip and rinse" approach and compared to each other regarding their ability to minimize nonspecific interactions with proteins is compared. It is demonstrated that polymer coatings approach the performance of fluid lipid coatings with respect to minimizing these interactions. Moreover, these polymer coatings enable accurate estimates of the volumes and spheroidal shapes of freely translocating proteins; uncoated or inadequately coated solid-state pores do not have this capability. In addition, these polymer coatings impart physical and chemical stability and enable efficient and label-free characterization of single proteins without requiring harsh cleaning protocols between experiments.