Tuck pointing old chimney help

I have an old large chimney at my cabin. (Very large stones like an old building foundation.) It is need of some TLC, tuck pointing to be exact. My question is…..is there a good box store product for this? I want to make sure it is weather/water proof. I am sure there are mason’s that know of some complex mixtures….I am looking for a good DIY type of product. Something that will do the job but not too complex.

What type of stone is it? And is the old mortar disintegrating into sand?

I think it is sandstone. And yes....some of the mortar is breaking down. Cabin was built in the 1930's.

How is the condition of the stones? Faces or edges spalling or popping off?

Typically you want the thing holding the stones together to be softer then the stones, problem is that sandstone is pretty soft and just about any cement based mortar is harder then it. That would leave lime based mortar but that is not a premix that you buy in a big box store.

If you do go the big-box cement based mortar, use the Type-N premix mortar. Its a lot softer then the Type-S

Avoid big box, go to a masonry supply place.