That's the exact same thing I'm using, it's working well. I'd say start off at the base line level for seedlings, then work up from there. The seedling level of 2 grams/gallon seems to do fine with most everything.

As you get above 2g/gallon, just watch for nitrogen toxicity. Too much nitrogen means you need to lower the feed level when you're using mega crop.

I've never made it above 3 grams per gallon of mega crop, and I'm going into my fourth week of flower right now. I'm actually back down to 2g/gallon right now, but I'm also watering 5 times a day under 500w (actual power draw) of Chinese quantum boards in a 4x4 tent.

As for bud explosion, it seems to be working, but this is my first grow, so I really have no idea. I'm currently at 0.4g/gallon, and the plants are looking okay-ish right now as far as P and K go. Did have some signs of P and K toxicity at 0.6g/gallon, and had all sorts of exciting problems when I tried to do the suggested 1g/gallon initially. I'd say start out at half strength and work up and you should be fine.

So far, I do really like mega crop. For an all in one nutrient, it seems to do pretty well.

Figured I'd try to upload some pictures, so you can see what Mega Crop and Bud Explosion can do with a novice grower. I also add "Real Growers Recharge" to the feed water once a week.

This is right after I transplanted them into coco coir - they had been in dirt in solo cups for a couple weeks at this point.



Vegged for about 5 weeks, this is what they looked like when I switched to 12/12. Really should have gone to 12/12 sooner.



After two weeks of flower, this is where they were at. Started using Bud Explosion right when I switched to 12/12, probably didn't need to, but it doesn't seem to have hurt them.



Should probably note, I lollipoped them at the end of the first week of flower. I also defoliated them at the end of the second week of flower. Did a decently harsh defoliation, this is what they looked like after.



After a week, they were pretty much back to normal. Still just using Mega Crop and Bud Explosion, along with Recharge once per week.



And finally, where they are today - at the end of the fourth week of flower, after taking off a few more leaves.



Should have about four more weeks left on them as far as I know, maybe a little longer on one or two of them.

Again, this is my first grow, and I have basically no idea what I'm doing, and these are my results, using Mega Crop, Bud Explosion and Recharge. If you've done a few grows and know what you're doing, I'm sure you can do better.