I am assuming that after this crack filling process, you are going to completely repaint... You should.
In my opinion, latex caulk will be one of the best ideas IF the cracks are not too wide.
Most of the cracks will now act as expansion joints for the house and you will see a majority of them re appear with the moisture content of the soils with the seasons.
And, the part about latex not bonding to alkyd paint, I have never heard of, but that does not mean anything. Actually the latex will be forced into the actual crack to go as deep as possible and to be leveled off with the surface, so actually the latex is not near any paint. The latex will act as a rubber band if you will and will expand and contract with the cracks and not crack again as fast.
I would then recomend a good quality 35 year latex/silicon paintable caulk for this process. Cut the end of the caulking tube at a 30 degree angle and very close to the top. This way you can hold the tube close to the crack and pump caulk into the hole until it oozes out. Do not worry about the ooze.
after several cracks are filled, then get a small saucer of alcohol, rubbing and then dip your finger in it and go over the caulking that oozed and this will smooth it out. any excess wipe off, but do not gouge the crack. You want the caulk even with the surface.
Do all the cracks in this manner and then after a day or so, go back and re paint.
This process should work up to cracks 1/4 inch or less wide, not long.