Drop whatever gear you normally carry that you don't need on the trip (watch out for random encounters), use str-boosting or carry-weight boosting stuff, use the built-in speed-up thing, use the under passages to get around, and select your loot intelligently. Like, heavy inexpensive items should be recycled, excess scraps should be made into advanced repair kits and sold, make sure to repair expensive items before selling them if the math adds up, only carry what you think you can sell in one or two trips, carry a variety so you can hit all the vendors. I like to take my jetski into core city docks, sell jetski parts, go to the merchants and on lvl 3, then up to marty, then down to metro and walk the railroad to foundry, then walk back up the railroad and split off to rail crossing, then take the underpassages to free drones base (if you went with them) and then blaine/SGS, then take the ferry to junkyard and back, then take the underpassages back to core city and the docks back to my jetski. Takes like 10-15 minutes.