Rule of Thumb Concrete Mix Ratios

[arco_iris]

In the past I have left it to builders to mix mortars, concrete footings, pointing of stone walling, etc. and don't know what they do, by their experience. The internet is a bit Greek on the subject.

Circumstances dictate that I have acquired use of a Belle Minimix 150 mixer & need to fill a rough trench for footings of a 6ft. stone wall, the builder is unavailable.

If I order a BAG of All-in-one (paperwork says 850kg) how many bags of Cement do I need, and how do I mix it .... ratios.... in simple terms of how many shovels of each and how many buckets of water?

Does a foundation need any additive?

[aeromech3]

As a DIY watching and helping my Bricklayer build my wall; your aggregate is about 0.5 cu mtr and mix should be around 5:1 by volume so you need 0.1 cu mtr of cement which is about 140kg or 6x25kg bags.
Method: 5 shovel loads of aggregate into rotating mixer followed by 1 shovel of cement, start again 5 aggregate and then 1 cement until the mixer is comfortably loaded; have buckets of clean water ready and after a dry mix period slurp in until the mix is fairly dry still, it does not take a lot of water at this stage but the stew should not climb up the sides and yet not slosh at the bottom. Additive only in winter conditions.
Think you should wait for a Pro to add comment!
Is it 6ft high or long have you worked out the depth width of footing?