The download link for the practice rom can be found here.
Download SDCafiine as seen in the NSMBU Practice Rom Tutorial
Put the downloaded ZIP above into the SDCafiine that is on the root of your SD Card
Boot up SD Cafiine via the homebrew channel
Boot up New Super Luigi U
Replace the name of the folder (0005000010142300) with:
0005000010142400 for the European Standalone Version
0005000010142200 for the Japanese Standalone Version
000500001014B700 for NSMBU + NSLU US Version
000500001014B800 for NSMBU + NSLU European Version
(These versions are untested so if they do not work please let me know via my contact methods on the About tab)
Make a folder called sdcafiine on the root of the SD Card (if it doesn't already exist)
Make a new folder in the sdcafiine folder called (if it doesn't already exist):
JP: 0005000010101C00
US: 0005000010101D00
EU: 0005000010101E00
In the folder with the NSMBU title ID, make folders that go Practice Rom (you can use the one given in the NSMBU practice rom if you want) -> aoc -> 0010 and then in the 0010 folder move the course_res_pack folder from the practice rom install there (the final path should be sdcafiine/[Title ID]/Practice Rom/aoc/0010/course_res_pack where Title ID is the name of the folder you made earlier in sdcafiine depending on your region).
(The JP and EU versions are untested so if they do not work please let me know via my contact methods on the About tab)
Note: If you are using NSLU as DLC and installed the practice roms, you should delete the folder titled "US" in the [Title ID]/Practice Rom/content folder, otherwise some text for menus will be broken or not present.
This is currently pretty limited but its features include:
Warp pipes to the boss of every tower and castle
Entering 7-Tower spawns you at kamek
Entering the final level in world 8 spawns you right next to the final bowser fight
Loop pipes for the elevator level in world 8
The download link for a version of 8-C2 that has warp pipes at the beginning and end of the 1st room that takes you directly to Bowser can be found here.
The download link for a version of 7-T that has a warp pipe at the beginning of the 1st room that takes you directly to Kamek can be found here.
To install either of these, simply locate the course_res_pack folder in the practice rom directory and replace the existing files in there with these.
This was entirely made by me, Saria_100. This also might get updated at a later point with more features.