Actually it's correct to shift down lower gear + applying some brake when U doesn't want to burden the brakepad and tyres.....

and in case if you are on high speed and want to slow down ur car asap, follow what did Don^Don said .....for me, If I'm in the 5th gear mode, I will shift to 3rd gear and release clutch + hit the brake harder than usual...and hence I quickly change to 2nd gear + brake...afterall, It's depend on ur driving skill....when U shift to lower gear and U feel the car starts lowering the speed b4 ur meter hit high RPM, that is the moment U need to apply much brake....this will decrease ur speed lots....