it is an horrible job to do so price well the chemical from tensid are enviromentally friendly but they burn skin badly, make sure you wear protective clothing gloves and face mask when using the chemicals, also make sure all glass and metal door handles etc are protected as the chemical will damage them.
It is a two chemical job, first the degreaser is applied by brush this is an heavy alkaline cleaner and has to be used to remove grease before the acid applicatiion can work, this degreaser is left on for about twenty minutes and then powerwashed off, next the acid is brushed on left to dwell for again about twenty minutes and then again powerwashed off some areas if particularly bad may need another application of acid.