Credits to swinch, Claude, grass, Alanim, and Mill
Because SMRPG's RNG counter always follows the same pattern from power-on, and only runs inside world areas and battles (not in the file select menu or on the overworld map), making a save very close to the Knife Guy / Grate Guy fight allows us to use Rock Candy at specific points in the battle to guarantee freebies.
Claude's tutorial video outlines three different methods of performing the Rock Candy manip.
You can opt to manipulate 2 freebies, 3 freebies, or 4 freebies.
2 freebies is the slowest and easiest to perform, 4 freebies is the fastest and hardest to perform.
The position of the save box during its float animation at the time you opt to jump on it will matter, as Mario's saved Y position can affect the timing that you enter the fight. This is especially important for the 4 RC manip.
You can opt to find audio cues that work for you in performing this manip.
As explained in the tutorial, grass has built a tool that you can use to hit the frame windows. Initiate the timer at the same time you load your save file.
Despite its page title, use of this tool is not banned.
Here is a list of indicators to tell you if you were early or late on an input, for inputs where an enemy gets a turn immediately afterward.
MARIO RC:
7-8F EARLY: Physical on Koopa
5-6F EARLY: Physical on Mario
3-4F EARLY: Physical on Geno
1-2F EARLY: Sleep Bubble on Koopa
10F CORRECT: 2298 - 2307
1-2F LATE: Physical on Mario
3-4F LATE: Sleep Bubble on Koopa
5-6F LATE: Physical on Geno
7-8F LATE: Echofinder on Koopa
MARIO RC TEXT CLEAR:
7-8F EARLY: Echofinder on Geno
5-6F EARLY: Echofinder on Koopa
1-4F EARLY: Echofinder on Geno
1-4F CORRECT: Physical on Koopa
5-6F CORRECT: Physical on Mario
1-4F LATE: Sleep Bubble on Koopa
5-8F LATE: Echofinder on Mario
MARIO PUNCH:
1-2F EARLY: 116
CORRECT: 128
CORRECT: 128
CORRECT: 128
CORRECT: 122
CORRECT: 122
CORRECT: 126
CORRECT: 132
CORRECT: 122
CORRECT: 126
CORRECT: 122
CORRECT: 128
CORRECT: 132
CORRECT: 126
CORRECT: 132
CORRECT: 128
1-2F LATE: 114
GENO 1ST RC:
7-8F EARLY: Juggle attack on Koopa
5-6F EARLY: Juggle attack on Mario
1-4F EARLY: Juggle attack on Koopa
4F CORRECT = RC Freebie
1-2F LATE: Juggle attack on Koopa
3-6F LATE: Juggle attack on Geno
7-8F LATE: Knife throw on Mario
MARIO RC
7-8F EARLY: RC Freebie
5-6F EARLY: Echofinder on Koopa
3-4F EARLY: RC Freebie
1-2F EARLY: Sleep Bubble on Koopa
4F CORRECT: RC Freebie
1-2F LATE: Echofinder on Koopa
3-4F LATE: Sleep Bubble on Mario
5-6F LATE: RC Freebie
7-8F LATE: Sleep Bubble on Mario
MARIO RC TEXT CLEAR
3-4F EARLY: Echofinder on Koopa
1-2F EARLY: Sleep Bubble on Geno
1-2F CORRECT: Physical on Koopa
3-4F CORRECT: Physical on Mario
1-2F LATE: Echofinder on Mario
3-4F LATE: Echofinder on Koopa