Hashtag retweet is used by botted channels for community's like #Java #Android ...
But recently I have seen some doggy channels using it with likes and comments.
To be able to do that you have a choice between native api ( normal v2 or premium ) and browser automation.
For the api solution is very straightforward ( search for #Hashtag take the last tweet > follow/retweet/like/comment )
Next is the browser automation , you need to submit a search , render the webpage to html by yourself programmatically , fulfill the comment click() retweet and like , and the most important is to calculate the last job to avoid duplicate task.
Now who is better?
Api of course
End.
The browser automation can be used Without hurting the main account and do the same job with opportunity to abuse the system.