Hi,
I may not tried yet Island but I feel it should be similar in term of McMmo. Here some tips on how I does mine:
1. /skills will show you current level for every specific McMmo skills, always go for the lowest one.
2. Spread out your grind into multiple skills. This means instead of leveling Mining to 2k at one go, try doing 200 on Axes, 200 on Archery, 300 on sword. It is always faster to get skill level by this instead of grinding for one high level skills.
3. Make /party. Party gives you more Xp than solo grinder, but you have to make sure everyone grinds, no free Uber mmo rides.
4. Combine grinding. Personally, I have tried leveling 5 skills at the same time, and it does work. Skills like brewing, taming, mining, repair, woodcutting can be combined and grinded at the same time, provided that you know how to setup your "stations". It is up to your creativity on how can you achieve that.
5. Make a machine that can reduce the effort you need. Brew machine, acro machine, and so on. Find a pattern on how to maximize your mcmmo level.
6. Use /mmodebug to find out what you need to obtain the biggest Xp for that skills.
7. Info sharing. Some people thinks that sharing info about specific skills to the public tend to make them loss, but trust me, all information I acquired wont be possible if I didnt share my intel. You dont know what I know, I dont know what you dont know.
Anyway thats my suggestions.
Wish you the best of luck!