The following two verses both discuss the fistful procedure of the meal offerings:
• Verse Lv06-08b states And he shall take up therefrom
  • with his handful,
  • of the fine flour of the meal-offering,
  • and of the oil thereof, a
  • nd all the frankincense which is upon the meal-offering,
  • and shall make the memorial-part thereof smoke upon the altar
  for a sweet savour unto HaShem.
• But verse Lv02-02 states And he shall bring it to Aaron's sons the priests;
  • and he shall take thereout his full handful
  • of the fine flour thereof,
  • and of the oil thereof,
  • together with all the frankincense thereof;
  • and the priest shall make the memorial-part thereof smoke upon the altar,
  an offering made by fire, of a sweet savour unto HaShem.

Notice the distinct underlined words - with, full - in each passage. From these words Rashi learns:
• With his hand emphasizes that he should use his own hand to scoop it up but not a special utensil.
• full handful emphasizes that the scoopful should not overfill or underfill his hand.

Advanced Rashi: We make two inferences from the alignment. The inference from the word his is found in the Rashi comments on Lv06. The inference from the word full is found in the Rashi comments on Lv02.