A method and a system and a container system for transferring separation resin from at least one first container (3; 3; 3a, 3b; 3a′, 3b′, 3c′, 3d′) to a second container (5; 5′), wherein said first container is a deformable, single-use separation resin storage container, said method comprising the steps of:—preparing (S1) the at least one first container by providing a deformable, single-use container comprising an outlet port (4′) with a predefined volume of separation resin in a storage solution;—fluidizing (S3) the separation resin in the at least one first container to provide a resin slurry, said fluidizing being performed by mechanical interaction to the first container from an outside of the first container to provide a deformation of said first container;—fluidically connecting (S5) the outlet port (4′) of the at least one first container to an inlet port (103) of the second container;—transferring (S7) separation resin from the at least one first container to the second container by generating a pressure difference between an interior of the second container and an interior of the first container where the pressure is lower in the second container.