Does anyone notch trowel both the tile and the substrate?

[GoneGuy]

I always back butter any tile bigger than metros, with troweling both the substrate and tile I trowel both in same direction to prevent any air getting trapped

 

[Paul Giovanni Raimondi]

I always back butter, I always spread the back of porc. tiles and wall with flat trowel before using notched side and will always use a 4mm notch on back of tile if over 60x60. But I’m not a tiler.

 

[hmtiling]

Some tiles need skimming to fill holes or pits. Like tumbled marble.

Most tiles don't required back buttering if the substrate is flat and has been prepped well.

You might need to back butter corners of tiles that change thicknesses like slate etc. You start tiling with the thickest of the lot, and in the lowest corner of the floor then.

Nearly all tiles don't require applying adhesive to the floor and the tile.

And pretty much all wall tiles don't require it. Unless the wall is rough in an area or something.

Got a picture of what you want to tile?

Totally agree with local. Not the best advice.
What about surface contamination, pitts and hollows on the backs of a lot of tiles. Solid bed is essential externally and in wet areas and without back skimming not easily achievable. Not to mention the difference in bond strength

 

[Boggs]

Same here, back butter anything bigger than a metro.