Adding Sugar during fermentation

There is a whole bunch on info as to why or when you should add sugar to your batch during fermentation, but I can't find anything that explains the process of doing so. I boil the sugar with water and then let it come back to room temp. Do I wait until there is no activity in the primary? When adding the sugar do I stir it in to the beer, or do I just pour it on top and cover it back up again? Any assistance with this would be greatly appreciated.

It is discussed here and I explain how I do it.

https://www.homebrewtalk.com/f163/f...ravity-long-fermentations-194587/#post2261246

Hi all!

This is my first post and I have a question about my first brew. I am home brewing Brewferm's Grand Cru (9 litres) and it has been fermenting for about 2,5 days now (around 60 hours). Because I am located in a tropical country the fermentation temperature is a bit higher than what is recommended in the recipe (around 29 C instead of 25 C recommended). Also my pitching temperature was around 28 C. There was a lot of activity in the first 24 to 36 hours. But after 48 hours the krausen fell and activity has decreased.

I have read quite a lot of threads before posting and didn't find a definite answer so that's why I am posting again in this thread. I hope it's ok.

When I was re-reading the recipe I realised I added the wrong amount of sugar to the wort (I added 110g instead of 500g). My OG was 1.057 vs an indicated OG of 1.075 in the recipe. My guess is that due to the high fermentation temperatures and the fact that I added much less sugar than needed, the yeast was quite quick to consume all the sugars.

So my question is, should/can I add the rest of the sugars to the brew at this point? (around 72 hours after pitching)
If yes, then how should I add it? Dissolve it in room temperature water (how much) and then mix it carefully with the fermenting beer?

Thanks in advance for your help!