A method for preparing a gas separation membrane system, wherein said method comprises: (a) depositing a layer of gas-selective material comprising a gas-selective metal upon a surface of a tubular porous support, having a longitudinal axis, to thereby provide said tubular porous support having a gas-selective membrane layer; (b) annealing said gas-selective membrane layer to provide a first annealed gas-selective membrane layer; (c) providing a first abraded membrane surface by polishing said first annealed gas-selective membrane layer under a first controlled polishing condition with use of a belted abrading medium defined as having a centreline that further includes a structured abrasive article comprising a backing having bonded thereto an abrasive layer comprising a plurality of shaped abrasive composites that comprise abrasive grains dispersed in a polymeric binder; and (d) placing a second layer of gas-selective material comprising a gas-selective metal upon said first abraded membrane surface to provide a first overlaid membrane layer, wherein said polishing is performed with a robotic polishing unit, and wherein said first controlled polishing condition parameters include: a first belt speed, which is a linear rate at which a fixed point located on the centerline of said belted abrading medium moves relative to a starting point fixed in space on the centreline, wherein the belt speed is in the range of from 0.005 to 5 metres per second (1 to 1000 surface feet per minute (sfpm)), a first part speed, which is a rate of a number of turns of said tubular porous support completes in one minute around said longitudinal axis in revolutions per minute (rpm), wherein the part speed is in the range of from 20 to 600 rpm, a first lateral speed, which is a linear rate at which the centerline of said belted abrading medium and its contact point with said tubular porous support moves in parallel with the ground in millimetres per second (mmps), wherein the lateral speed is in the range of from 1 to 60 mmps, a first contact angle, which is a position at which said tubular porous support is held in contact at a point of contact on said belted abrading medium, and a first repetitions set, which is a number of full polishing motions with said belted abrading medium, wherein a full polishing motion is when the belted abrading medium remains in contact with the tubular shaped porous support and passes along the one full length of the tubular porous support from one end to the other end and back again. (a) depositing a layer of gas-selective material comprising a gas-selective metal upon a surface of a tubular porous support, having a longitudinal axis, to thereby provide said tubular porous support having a gas-selective membrane layer; (b) annealing said gas-selective membrane layer to provide a first annealed gas-selective membrane layer; (c) providing a first abraded membrane surface by polishing said first annealed gas-selective membrane layer under a first controlled polishing condition with use of a belted abrading medium defined as having a centreline that further includes a structured abrasive article comprising a backing having bonded thereto an abrasive layer comprising a plurality of shaped abrasive composites that comprise abrasive grains dispersed in a polymeric binder; and (d) placing a second layer of gas-selective material comprising a gas-selective metal upon said first abraded membrane surface to provide a first overlaid membrane layer, a first belt speed, which is a linear rate at which a fixed point located on the centerline of said belted abrading medium moves relative to a starting point fixed in space on the centreline, wherein the belt speed is in the range of from 0.005 to 5 metres per second (1 to 1000 surface feet per minute (sfpm)), a first part speed, which is a rate of a number of turns of said tubular porous support completes in one minute around said longitudinal axis in revolutions per minute (rpm), wherein the part speed is in the range of from 20 to 600 rpm, a first lateral speed, which is a linear rate at which the centerline of said belted abrading medium and its contact point with said tubular porous support moves in parallel with the ground in millimetres per second (mmps), wherein the lateral speed is in the range of from 1 to 60 mmps, a first contact angle, which is a position at which said tubular porous support is held in contact at a point of contact on said belted abrading medium, and a first repetitions set, which is a number of full polishing motions with said belted abrading medium, wherein a full polishing motion is when the belted abrading medium remains in contact with the tubular shaped porous support and passes along the one full length of the tubular porous support from one end to the other end and back again.