Good to see people using lime on old masonry. I’ve written a book on the subject.
As to mixers, ideally one should use a “pan mixer” but they aren’t often offered in many bricos. The ordinary type of mixer works best if you remove the blades, as it allows the mic to “roll over” not unlike making a meringue! As the machine rolls, the mix peels off and “splats” onto the bottom, which is the proper way to mix lime.
Unfortunately, a lot of Brit immigrants still use the cement/ lime mix, but they use the wrong lime! On the shelves of UK and Irish builders merchants the lime offered in plain “hydrated” which isn’t hydraulic. The equivalent hers is " Chaux aérienne" (air lime), which isn’t readily available in bricos. When they ask for lime, they end up with NHL 5 and add it to the cement, making the mic even stronger. The cement/lime mix in the Uk is not recommended any more, except for new build.
What a lot of supposed tradesmen don’t know is that cement mortars and concrete have the same characteristics as steel, and contract/ expand with temperature, while the lime mortar/clay (agile) built walls don’t move at all, except for natural subsidence, resulting in severe surface cracks and internal damp.
Have you ever used lime concrete?
regards