Three suggestions:
1) Use an quick interior detailer like Meg`s Quick Interior Detailer spray (available over-the-counter at Walmart) or better, Nextzett (formerly Einszett) Cockpit Premium Spray cleaner for interior wipe-downs, including leather. Just remember to spray it on an applicator (Cotton cloth or microfiber cloth) OUTSIDE the interior and not directly onto a surface.
2) For vehicles parked outside 24/7 (un-garaged for the most part), use a long-lasting wax like Collinite 476S or Finish-Kare`s FK1000P Hi-Temp (Sometimes referred to as Great White) wax. Yes, it`s a lot of work to hand-wax a vehicle, depending on size, BUT if you do this twice a year (early spring & late fall), your clear-coat (assuming they are vehicles less than 20 years old and not white Toyota`s, because older vehicles & white Toyota`s MAY have single-stage paint and NOT be clear-coated) will last (IE, not be as susceptible to clear-coat failure from sun oxidation or acid rain/environmental fallout) much (as least in my opinion) longer than with spray waxes.
3) When washing using a 2-bucket method, try using an electric leaf-blower to blow off excess water after final rinse. Just be careful you do not touch the vehicle surface with the nozzle end OR that you have used the blower as a vacuum to suck up lawn grass or leaf debris, if the blower can be used as such.
Gas-powered blowers COULD be used, but they are heavy and difficult to hold up to the roof of a vehicle. Getting water out of "inaccessible areas", like side mirrors, gas filler door/lid, side trim moldings, front egg-crate grills and headlight/fog lamp gaps, door jam gaps, and wheel rim spokes and lug-nut holes are a real time-saver.
In an effort to reduce water spotting, wash the vehicle body (side panels, front grill/bumper, back bumper, and windows) exterior and door jams first and dry. THEN wash the wheels (tires and rims) and wheel wells next, rinse and dry ONE AT A TIME (remember leaf blower suggestion). This is especially true on warm, dry, windy days. You may even need to find yourself doing the top (roof, windows, and hood) FIRST, then having to rinse and dry them, THEN do the rest of the vehicle`s sides NEXT and door jams after that, then finish with wheels. I find that if you wash,rinse and dry too fast of an entire vehicle to prevent water spotting, you will miss MAJOR dirty areas. If the vehicle is REALLY dirty,(like from an off-road or dirt road excursion) you may need to wash the sides and wheels first and throw-out-and-refill the bucket wash soap-n-water and bucket rinse water frequently.
Best suggestion? Get a gas small engine-powered pressure washer and foam gun. Your washing/cleaning of four vehicles on a (very) regular basis would greatly benefit that and the time you save and thoroughness of vehicle cleaning will pay for itself, not to mention the other household tasks the power pressure washer could be used for (like brick/vinyl house siding or glass windows, cement driveways/walkways, lawnmowers, and boats/4-wheelers/trailers/RVs). It`s also a nice "bartering chip" to use with neighbors for borrowing their tools or utilizing their services for "free".
