Getting PostProcessInput Textures as Input to Custom Material Nodes in 4.27

I'm trying to do a custom material node to apply a Gaussian blur. There are a few how-to web sites that show how to do that, but their HLSL code doesn't work.

They all break at sampling the scene texture. The compiler doesn't recognize the SceneTextureLookup function used in some old code.

Using Texture2DSample take 3 inputs, a texture, a sampler, and the coordinate. If you input a texture to your custom node, the sampler is automatically generated.

I think, PPI_PostProcessInput0 is the texture to sample, but I can't figure out how to get its sampler.

Edit: If you make a variable called "SceneTexture" in you custom node and connect the SceneTexture:PostProcessInput0 color output up to it, you then have access to SceneTextureLookup. I thought you'd only get the float4 value returned.