"I feel your pain". Our present camper (2017 Rockwood Ultra Lite) was ordered with awnings on both slides. Kind of pricey, but worth it. The previous camper we owned had one slide with no awning. I've used them all...towel, mop, leaf blower etc. to remove standing water or crud. As stated earlier slide toppers don't stop all the problems but in my humble opinion they are a big plus.
2017 Rockwood Ultra Lite
2014 Silverado 1500 4X4 5.3L 3.73
“Not all those who wander are lost.”