A system includes a gravity-feed spray coating device having a body with a liquid inlet, a handle coupled to the body, a spray head coupled to the body, a liquid passage extending from the liquid inlet to the spray head, and a gravity-feed container fastener disposed adjacent the liquid inlet. The gravity-feed container fastener includes a non-compression container fastening mechanism. The system also includes a first gravity-feed liquid supply container having a liquid outlet and a compression fitting adapter, wherein the compression fitting adapter compression fits the liquid outlet to the liquid inlet without the non-compression container fastening mechanism.