I use a thin layer of dielectric grease on each of my (supposedly) waterproof higo wiring connections. Just a teeny dab. For thingds like throttle and display while riding in the rain, I use bags and rubber bands, with an eye towards protecting the device itself, and wherever the cables go in from direct spray. To a point, Saran Wrap or similar wrapped over itself can work better on a throttle or PAS panel than a ziploc bag and rubber bands. Best to just experiment and see what holds up better during use.Have any of you tried spraying some of your electrical components with a film that waterproofs electronics?
If your display is not IP65 or better, a dab of silicone weather sealant or Shoegoo that is then formed to wrap around the cable ingress point makes for a permanent seal. This works particularly well on Bafang hub motors whose cable runs straight into an unsealed motor thru a hollow axle.
After many years, have never had an electrical connection issue from water ingress. I did have a really lousy Saturday when I opened up a hub motor and saw it was all orange inside from water coming in from the hollow axle. But a few hours and a tub of elbow grease later it was good as new.
You want to take care not to create a drogue chute back there. Lots of wind will come back over and around the sides of a bike on the back of a car vs. a full size motorhome. Best to approach the task as you have by working on individual items and don't try and cover the whole schmeer.Also, do any of you while transporting on bike rack completely cover your bikes? I see them covered on the back of RVs sometimes.