Its easier for people who speak Mandarin to learn Cantonese, but other way around? Whats the best way to learn Mandarin without the Canto accent.

Well mandarin actually has a few accents of its own. I know one distinct mandarin accent which sound like an R is at the end of every word.

Either way, once you learn mandarin even with the canto accent, you can figure out what everything else is pretty easy

I actually think it's the other way around. I'm a Cantonese speaker and I don't find it that hard to speak Mandarin or learn the tonal differences. After all, Mandarin Chinese has 2 less tones than standard Canto so if anything it should be easier for a Cantonese speaker to learn Mandarin. My accent sometimes comes through across naturally, but I think it's easier to spot a Mandarin accent in Cantonese. That's just my experience though.