do you use any kind of tool or service to prepare you product hunt launch? Something that make screenshoot or logo for you?

Maker of WIP amongst other things.

Nope. I'm not sure how a tool would know how to best market a product?

For screenshots I tend to set a nice background wallpaper, and then take screenshots using macOS' built-in screenshotting tool. You could also use @lukaszmtw's CleanShot which makes this process a little easier.

For the icon I tend to use Photoshop to make a simple animated GIF. There are some tools that make this easier (e.g. I remember there being a tool to easily create a GIF of different emoji), but typically it's up to you to create something that best communicates your concept.