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

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.