It is definitely not an easy technique to learn, but if you're going fast enough to allow them to clash together, it's fair to say you're relatively new to the drums. If not, skip to the last few bits.
Firstly, don't practice everything so fast! Bump the speed up as you improve, not as you just start. Everything is difficult at a fast tempo (except for double whole notes, but that's besides the point), so start slow.
Secondly, if you are new, don't start working on playing double bass drumming quite yet, you'll develop bad habits and use it as a crutch. Make sure you use your dominant foot EXTREMELY WELL before moving to double bass. Not only will your right foot's dexterity improve double bass in the future, but you'll be much more capable of using open/closed high hat, which is what your right foot is really before. Double bass drumming is fun, but it's not important.
In case you skipped that whole bit, go at a slow tempo. Everything will clash together at first, like as a beginner where if you tried perfect flams at a fast tempo, they would always fall flat, right? It's the same aspect with double bass. Try starting at 88 bpm and just playing 1+2+3+4+1+2.... Or RLRLRLRLRLRL.... Remember, in almost every circumstance, using your right is preferred, you should be able to use your high hat with the left.
Once your getting good at just single stroking, trying doing different rudiments such as paradiddles, flams, double strokes (no bounce, sorry), among others. This will improve the coordination in your feet, thus increasing your speed, evenness, and maybe even being able to do complex rhythms on the bass drums while playing normally. If you get the chance, listen to the drummer from Tool, Danny Carey. He practices snare drum rudiments and solos... With his feet. That's not even 5% of what he can do, either. Check it out.
One final thing I'll leave you with is one of my favorite, simple exercises. Start single stroking with your feet, eighth notes at first. Next, add your hands doing paradiddles, either single, double triple, whatever you want to. These should be eighth notes as well at first. Now, once you've figured this out, start doing sixteenth notes, triplets, mix them up, like sixteenths with your feet and eights with your hands.
Best of luck to you, it's a tough thing to learn.