plastic dipping esc and servos is good

i use blue silicone
or plastic dip in can. you need dip the thing and let dry before use,. like esc, mount of the fan
dip it
let it dry
mount the fan
you need use all cables when dipping if it is a ESC that is sensored also

mount them to your rig to make it waterproof after,. like sensorcables from engine to esc, have it on when you dip esc
you can add silicone at the motor later where you put the sensor cable. Silicone around the connector abit.
you need add more everytime you need release cables if you need fix diff or something service with your car.

enjoy

Most easy is have weather cover, dust proof nylon cover, if there is one made for your car to protect whole chassie from sand and wet
impregnent that sometimes waterproof spray it sometimes

bonus tip:
use wd40 or electic crc spray, spray all electronics in side first with this, take towel and dry off .
make an anti corrition service before you dip is very good
then the esc last long time

this is something you can do with old stuff that you dont care about so much
also when warranty is passed .

Also only for bashing. and for fun cars that you have extras, drive for fun only, not serious basher car, the extra old cars only, you dont care alot about

If you race at track, or bash very serious often with your car
Buy new waterproof stuff