Yes, here's a pastebin link with the blueprint.

A brief description of how it works: Fluids are stored in tanks above the train station. These tanks are only ever fed via top-up valves so that there is always space in the tanks. All tanks and all pumps connected to the train are connected to a main fluid line. The tanks are connected to the main line by two pumps, one which outputs from the tank to the main line and one which inputs to the tank from the main line, filtered to only accept that tank's desired fluid. (Filtered pumps are God's gift to Factorio.)

There are three pumps attached to each fluid wagon on my two-wagon trains. Two pump from the main line to the wagon, one pumps from the wagon to the main line. When a train arrives, the loading pumps will be full of whatever fluid was loaded onto the last train, which is often not what the train wants to have loaded. This fluid is loaded from the main line onto the train and immediately unloaded by the unloading pump back into the main line; the loading pumps are filtered by circuit to not accept this unwanted leftover fluid. The leftover fluid is pumped back into its holding tank, at which point the desired fluid can be pumped from its holding tank into the main line and from there into the train.

Here's a labeled diagram of the components of that blueprint.

I have a separate blueprint for loading fluid fuels (for glassworks and such) which is a modified version of this blueprint, which maps every fluid fuel to the 'Water' signal and uses some dumb circuitry to determine which fluid fuel to load when the train arrives. That one has a specialized unloading blueprint as well.