I added slug input field in my custom post type and allow users to edit it at front end. Then, when insert post, I use this:
$wp_insert_post_args = array( 'post_status' => 'publish', 'post_type' => MY_POST_TYPE, 'post_author' => $this->creator_id, 'post_title' => $this->name 'post_name' => sanitize_title( $this->slug ) );
My custom post type already suports 'title', so, it suppose to auto generate post_name. Now I add $slug as 'post_name' as described above, will woredpress use 'title' to generate 'post_name', or use my 'slug'? will wordpress perform slug exist checking as it does on normal posts, or should I take care of the checking myself?