On the input section of the project settings create an input for button boost. Then in the skateboarder blueprint create a button press event for that boost button in the event graph. Create a float variable. If the float is >0 then apply the boost. Acceleration and or top speed is increased with an addition or set. Float variable is set to zero. Delay for 1 tick the amount of time the boost occurs. Reset speed/acceleration to original value. Delay the amount of time between being able to boost.
Is the simplest way. I have boosts on space ships. It’s good to also add a camera shake and or other effects right after the button press event.