The best way to bump a post is to post periodically, i.e. once a day or every other day, simply by comment "bump" or by giving any updates in the comment if you've changed something or added something to the main post. Avoid creating separate threads bumping other posts. This is done very, very rarely (a good example was the WW data bumping thread to keep bumps separate from the main thread that actively had users compiling and discussing data, thus avoiding confusion, clutter, and disorganization) and is otherwise considered spam.
It can be frustrating or disheartening to have minimal to no activity on threads, but it happens! Some posts attract a lot of attention and interaction, others don't. It's just how things go. We can only bump things periodically and responsibly to avoid drowning out others' threads and hope for the best, really.
Creating a ton of threads can also be very overwhelming to people who may or may not be browsing your threads specifically, as it can lead to them getting confused as to where to comment or where to interact or can even lead to people avoiding threads.
Personally, I only bump my sale/trade posts usually once a week or every several days unless I have an update to the main post.