In our case, our strategy was to not try and find a shortcut or hack to grow our sales. We just ground it out by cold calling/cold emailing, paid ads, etc.
The problem with shortcuts is they are usually not repeatable or scalable. For example, a viral video or website can provide a boost of growth, but you can't predict if the next thing you produce will also go viral.
What you want to find is a predictable way to generate sales where the economics work. The economics work if the cost to generate a sale is 1/3 or less of the lifetime value of the customer. Even if it takes a lot of effort to generate the sale, if you have a predictable way to generate leads, and you know how many leads you need in order to produce a sale, and you make a good profit on that sale, you are golden. You can then ramp up your lead gen and you know your sales with grow faster. It doesn't take any luck to display more ads, send more emails or hire sales reps.
This is just my experience... What has worked for your startup?
Yes, I agree with you. There are no shortcuts to boost growth that can sustain in the long term (may be that's why they are called "short" cuts!).
I would add customer referrals to your list. The key will be for the startup/business to provide a good customer experience that may result in leads. In my opinion, this is a minimum effort-maximum impact strategy that offers predictability if implemented well.