i don't know about this. constant drilling and not moving on until you know how to spell everything perfectly might work for some people, but it definitely doesn't work for all, and i reckon that the "drilling" learning method is responsible for culling about 90% of the people who take up greek. it makes it feel like you're not learning a language but are doing primary school maths homework.
many here far better than me at these languages probably have the opposite view, and it's good that both viewpoints are here in a forum after all. but if i had stopped to drill everything i would have stopped over a year ago... i hated maths homework
i've said this a few times, but the greek weren't all geniuses walking around with the instant natural ability to cite hundreds of word-endings on the spot--greek was just another language which people for hundreds of years could speak easily across the mediterranean. you can get to a comfortable level in greek without necessarily being able to spell every word correctly. i'm not saying to go faster through the same textbook, whcih would just mean skipping stuff. i mean concentrate on other parts of the language when sheer memorisation gets too painful--stuff which u have to teach yourself because they don't teach it in most textbooks--like greek's music and rhythm, standard phrases and proverbs, how the poetry works and sounds, different styles of writing like loose and periodic--these things aren't beyond beginners who don't know how to spell a word in the optative. rather it was learning about these things which made me keep going in greek, and made me later focus on getting the spelling right, when i could already read a bit.
i've said this before as well, but a problem with the traditional way of learning greek is that you can end up being able to say a lot about the grammatical properties of a word or clause, but you couldn't even string together a few short sentences on the spot to say something simple, even after years of study. i really think that so many textbooks don't teach greek; they just teach grammar using greek examples
. so that when people think about greek, they think "aorist, imperfect, optative, dative, apposition" rather than about greek itself. i've asked people who teach greek at uni after studying it since primary/high school to say something in greek and they side-step the issue. ask someone who started french 2 weeks ago and they'll happily bonjour you