i have personally used electric tape to cover spektrum rx, lipo connections, usb connector (mamba max) and the wires underneath the esc... not a permanent solution but for a few runs in light rain i did not experience any problems...
infact due to the cooler temps the car ran a few minutes longer using trak power 2s 5400mah lipo
i really think that esc's, rx and lipo should just come water proof