You are right IMO. No point training twice.

To help when he wees soak it into the paper and put the paper in the garden, then when you take him out the smell will act as an indicator.

Ignore any mess in the house (if you catch him midstream just say Uh Uh to interrupt him and sau Outside while taking him out) just clear it up and loads of praise when he goes in the garden. They do get it pretty quick as long as you give them loads of opportunity to do it in the right place.

It is worth using a word when they wee like "hurry up" it really does teach them to wee on command (i didn't believe that at first but it does).

Good Luck