Try using one of the newest versions of dolphin. They tend to have more accurate loading times.
Dolphin is never perfect however, and playing on console is the only way to get the most realistic practice.
There are ways to practice on Wii that help speed up practice.
For my practice, I use GCMM (Gamecube memory manager). I can use this app to load any save files from my huge library of .gci files onto my memory card.
http://wiibrew.org/wiki/GCMMUsing cheat codes is incredibly useful on Wii as well. Setting health to quarter heart, moon jump, superswim speed, void out anywhere, chest storage/door cancel anywhere, and map select make practice infinitely better.
https://gbatemp.net/threads/use-gamecube-cheats-with-neogamma.313218/