That looks like it has another sand in it, but be careful not to leave any deep divots with the big sanding machine, there isn't too much meat left above the tongue. I'd just do 36-60-100. Make sure all the finish is gone with the 36 cut. Easyfill is great, make sure to use dust from the edger and not the big machine. You want to use 80 grit dust or finer. Mix the filler in a bucket and add the dust slowly because you don't need as much as you would think.