Because of the booming popularity of audio and video, transcriptionists are finding work through a variety of different means. Many companies hire transcriptionists to turn their audio or video recordings into marketing or training materials. Video marketers (think YouTubers) may also hire transcriptionists to transcribe their recordings into written form so they can sell their services and products online. Law firms and government agencies also hire qualified legal transcriptionists to work for them.
The basic strategy is this: Post interesting content consistently with relevant hashtags. Use a service like Hashtagify for hashtag ideas. Follow users in your niche and engage with their posts. I also know a couple of people who grew their Instagram accounts quickly solely depending on shoutouts from influencers. You can use a service like ShoutCart for that or contact influencers directly (most of them list their email addresses in their bios).