My main app to design in is Figma but I'm equally comfortable using Sketch. They're apps similar to Photoshop but built for the specific purpose of designing interfaces.
When I show the designs to get feedback I’ll use Figma. I've used Marvelapp and Invision plenty but my preference is the former. They’re all great tools because you're also able to make interactive prototypes so the static designs can function similar to how the final website/app will end up.
Once the designs are finalised I’ll upload them to one of the services I mentioned in the previous paragraph, another option is Zeplin. They all allow a developer to look at the designs in more detail such as spacing between elements, colours, fonts and grabbing the assets.
This is everything a developer needs to start creating the app/site. My favourite is Figma because it covers everything and is a true all-in-one app.
Whether you have a solid plan or an idea, we can work to together to get it ready for development!
We can take your idea to a solid set of wireframes to give it some structure. Once your happy with those it’ll be time for some full mockups that you can pass on to your developers, present to your stakeholders or even use to get funding. If you already have wireframes and a solid plan I can work within that too, I’m happy to work in either capacity.
For communication on projects personally I like to use Slack but of course I’m not limited to it and can accommodate your needs if you want to use something else.