I was in a similar position once where I was bringing several developers up to speed. The most important thing that we did were constant code reviews, that is every commit was reviewed and commented on by everyone. After about one or two months they were not only picking up good practices but also felt confident with the codebase.

Also you could try and let your new developer write some test cases first for your project, so he is gets a feel for the codebase without breaking anything.

I was in a similar position once where I was bringing several developers up to speed. The most important thing that we did were constant code reviews, meaning that every commit was reviewed and commented on by everyone. After about one or two months they were not only picking up good practices but also felt confident with the codebase.

Also you could try and let your new developer write some test cases first for your project, so he gets a feel for the codebase without breaking anything.