Being a solo founder, how do you balance between product development and marketing?

Especially if you're a tech founder, it's a challenge to balance between doing R&D for product, development, testing, ship features while focusing on marketing (discussion, commenting, image/video editing, social media posting, being super active in Twitter and many more). For me, it's always a crucial step to hover on. I prefer to work on product one week and then work on the marketing the next week. This gives at least 40% focus on each side (I keep 20% for other tasks). Few things I do on a regular basis - like writing posts in Linkedin daily, without fail. LIke making a sort of habit to build an audience. Making a habit reduced the effort somehow. How do you prefer to tackle this hurdle?