Heres a free lesson.

Learn it BACKWARDS. start at the last measure, learn it, then learn the measure before that and keep going. That way, even if you dont play perfectly the measure your trying to memorize, you can keep playing and further solidify what youve already done. It sounds like it would be confusing but its not. Give it a shot.

memorize the x axis and the y comes pretty naturally

Memorizing music is really easy if you have a recording of the full band playing it. Listen to that until you get to know the melody really well, like you can recite it (helps if your director picked good music) and then play your part along with the melody. You will see how your part fits in with the music and automatically remember it when the time comes around to play it with the band. This really works for any instrument... but I find it best on snare.

While this may or may not be true for ease of memorization, I think learning parts this way gets your brain thinking about them all wrong. I encourage my students to have a solid understanding of what's going on rhythmically and dynamically (y-axis) before they worry about how to move it around (x-axis). It is better to be thinking "I have to play two sixteenth notes at 6 inches" rather than "I play a scrape from 1 to 2"

That's really good advice. I think I'll try that with the line one practice to see what happens.