That's the correct thing to use on heavy gunk deposits (never steel wool, sandpaper, or an abrasive eraser), but it will not cut oily film on tracks and/or wheels. For that and general cleaning, I use and recommend 91% isopropyl alcohol (not 70%, too much water). For the tracks, put 91% on a clean white cotton cloth, rub down your tracks with that keeping the cloth amply damp or moist (not dripping wet) and optionally follow that up with a clean dry cotton cloth. Do the same on loco and rolling stock wheels, but use Q-tips instead of a cotton cloth. I owned, operated, and repaired postwar and modern AF/L-AF handcars without the slipping you've described. I suspect that even though your tracks and wheels might look shiny clean after using the green Scotch pad, one or both still have a thin oily film on them you can't see. Note on AF/L-AF handcars, especially the postwar type, if you protect your engines with a purpose-built spike protector (not the kind in your power strips) the handcar can cause such a spike protector to throw itself down (cut power off from the tracks) b/c of how much sparking and arching takes place between its wheels and the track. That's sparking is due to their minimal points of contact, short wheelbase, light weight, and typically high operating speeds.