I wonder if you select restart race right after crossing the finish line in Star City so you begin the Silver Coin Challenge on that race without needing the T.T. Stomp or getting 46 balloons to enter.
The glitch in Hot Top Volcano is useful for trophy race.
I'm not sure doing that glitch to get to Jungle Falls during the Trophy Race is faster, I'm unsure.
100% route:
Balloon near Snowflake Mountain, Balloon near Sherbet Island, Wizpig, reset, enter code JOINTVENTURE for 2 players, Balloon near Dino Domain, Key in Ancient Lake, Tricky, Fire Mountain, Trophy Race, Trophy Race for Glitch, Taj, Snowball Valley for Trophy, Key in Snowball Valley, Bluey, Icicle Pyramid, Taj, Trophy Race for Glitch, Taj, Balloon near Dragon Forest, Whale Bay for Trophy, Key in Crescent Island, Bubbler, Darkwater Beach, Trophy Race for Glitch, Haunted Woods for Trophy, Key in Boulder Canyon, Smokey, Smokey Castle, Trophy Race for Glitch, Spacedust Alley for Trophy, Wizipg, ending.
Unlocking Drumstick and T.T. are not necessary for 100% completion, but to race as them, play from predefined save.