Handfeeding! Bucky turning his mouth away from Rumlow's hand, and maybe Rumlow forces his jaw open and kisses his cheek while he chokes it down, or maybe he waits until Bucky's too starving to refuse.

This is amazing?? Plus now I am imagining that Rumlow just fucked Bucky from the bottom, and now they're lying like that as Rumlow's come dribbles out of him. Rumlow strokes Bucky's hair and back, occasionally grabbing his shackled wrists if he starts to struggle too much, eventually stroking down to Bucky's waist and ass before dipping his fingers into his used hole. Slowly, gradually, with little breaks where he's just resting his fingers inside Bucky, he fingerfucks Bucky to another orgasm.

Also please consider that upon Bucky's rescue he could have: black eyes; bruises around his mouth from the gag; serious ligature marks on his wrist and ankles, and/or friction blisters from shackles; needle puncture wounds clustered on his arm, thighs and neck; bruises, lash marks, knife marks, bite marks, bootprints and handprints all over his body; hickeys; and yet be very clean and groomed, because Rumlow has been caretaking him.