Take a nylon brush and some powder solvent like
*Hoppe's No. 9
Place some solvent on the part and brush it like you were brushing your teeth. The majority of the fouling will come off. Cleaning every part until it is 100% clean is referred to as "White glove" gleaning. It is unnecessary.
Its a glock....clean it a little, lube it, slap it together and go enjoy it : )
This may help...