In my opinion, as long as you change oil according to PMS or shorter (4000klm) everything will be ok. If you think your oil sump is full of debris and contaminants, pulling down the oil pan is the best solution.
oil based engine flush. meaning oil din sya w/ detergents to removes slugde. try opening a can of STP amoy at kulay plang kerosene na kerosene na.
actually, no need para sa engine flush. just drain the oil overnight while the vehicle's tilted. or if you have the means, used compressed air to flush out the used oil in your engine.