I made prototype for app but came across (in my opinion) minor issues with flow of the app between the wireframes. I know this can be improved with a couple of changes but I am not sure what these changes are yet.
I've elicited feedback from people about it and have gotten overwhelmingly positive responses so I don't think these are critical changes but still want to iron out before development.
What is the best way to get feedback about specific ways to improve flow of app?
Chi chi try UXPin or JustInMind, both have great methods to attach notes, create requirements and ad tons of on events etc.
Often times choppy flow in wireframes is due to underlying issues in the user flow. Make sure you understand the business and user objectives before layering in the look and feel.
Great designs require lots of iterations. Try testing your wireframes by showing them to people as if they were using the final product. Give them a goal and look for places they get confused or stuck. If it is an option, an experienced UX designer could help you through the process.
In addition to pen and paper, I've had good luck with Balsalmiq. It allows creating and modifying rough ideas quickly, and the widgets are generic enough that you get feedback about using your product instead of feedback on your wireframing tool.
I'm a fan of Sketch + Invision. They have a plugin for sketch called Craft which helps you sync your designs from Sketch to the Invision app online where you can create click-through prototypes. You can use these to test before you develop them in your app. It is also a great place to host images and get measurements for your app developers.
I recommend moqups. You can attach notes to specific areas of the UI. You can also set up Interactions and run it in Preview mode, which makes it behave like a live app, so you can see how the flow works.
I recommend www.trillo.io (disclaimer, I am founder of the company, I will not promote it in answer if it was not directly related to the question.).