Use a special page to run a campaign to collect reviews. You can share the link on your social pages, include in your email campaigns, request review from your offline sales. When you are collecting reviews you can choose reviews as for your site or for a certain product.
As for recently purchased products, the Reviews product automatically sends a review request email to your customers.
Here is a link -
For example, we use this link on our demo site: http://ssw-demo.myshopify.com/pages/share-review
By default, it allows leaving a review to your site. But if you bypass 'product_id' variable then the posted review will be added to the product.
If you bypass 'email' variable then we won't request the visitor to log in for leaving a review. So there are no obstacles for a buyer to leave a review.
If you experience any problems then feel free to contact us