Hi Dale,
If you really want try and make them a bit more water resistant I would try the silicon plus heatshrink option. Probably heatshrink over the globe, small squirt of silicon in each end and then shrink it, wiping off the excess as it sqeezes out.
But a lot of effort and mess and I would not bother, standard low voltage light strings get rained on all the time and survive a year or three.
https://auschristmaslighting.com/ is a great resource for fellow Christmas Light tragics but I warn you it is a slippery slope into what can be an expensive hobby