Adding hashtags in your first comment
Adding your hashtags into your first comment is a common best practice for Instagram! It helps keep the focus on your post and caption when your audience is scrolling through Instagram, but still reaps all the benefits of using hashtags!
Instagram's API does not allow any third party app to schedule a first comment at this time.
However, you can use Later's Saved Caption feature to quickly add hashtags into the caption area of your post. That way, your hashtags are also copied into your clipboard when you open your post in Instagram.
When you paste your caption into Instagram, cut out the hashtags, post your photo, and then paste and post your hashtags in the first comment!