After doing this for a while I realized when looking at the Effort to result delta I have achieved the best results by just ballasting the sides of the plastic ballast then doing a thin even line down the center. Then the standard alcohol and glue along track center letting it flow into the ballast. As this happens then carefully filling in any jagged or displaced with pinches of ballast. Once dry, then simply airbrushing the ballast color I want, this unifies the plastic and rock bits to a uniform look. Then just brush painting the track and ties normally. Uses a minimum amount of ballast and avoids the endless battle of trying to get the tiny specks off the tops of the ties.
For fill I like to use sculptamold between individual double tracks after masking off the rail and ties. But in the past would sometimes use cheaper fill like scenery foam I wasn't thrilled with or spare WS ballast then cover with the actually desired ballast when dry. Just found sculpt easier though.
Example uses Kato double track.
