in Order to get this achievement you are going to need to play ALOT
you can, as said before play a song over and over till you get this but i find it easier to go for all the other achievements while you can(this varies with how good you are at the game)
Step 1: Play through Easy and 5 star everything(getting you 2 achievements, i would also recommend turning on left flip to get the "hendrix reborn" achievement as well)
Step 2:play through medium and 5 star everything getting you another two achievements
Step 3: play through hard and try to 5 star everything getting you one or two achievements.
Step 4:Play expert and try to 5 star if you can(if you can it will save you alot of time)
Final step: after 5 starring all difficulties or doing as many as you can, find a good group of 5+songs that you are really good at AND are high scoring(such as One, All nightmare long if you have it, number of the beast ETC)
after playing those songs a couple times everyday the achievement should come naturally(which makes you realize 100,000,000 is alot of points