JiffyLube, what
varnish did you use on your cap rails? How did you stir the
varnish before you applied it? Did you shake your varnish before you stirred it? Was the cap rail damp with dew or rain before you applied your varnish? Did you experience the bubbles after your first coat only or with the second and third coats etc? How did you apply your varnish? These might help us answer your question.
I agree it is helpful when varnishing teak and other oily woods like Ipe to wipe the raw wood with an appropriate solvent before applying the first coat of sealer or varnish. I'm not sure there is much benefit to wiping the work down with a solvent such as acetone or mek after the first coat with respect to the oil in the wood. I believe these are too harsh on fresh varnish and might cause you some problems.
I do wipe down between coats with mineral spirits or brushing liquid or turpentine but that is more to help pick up the fine sanding dust than remove any wood oils. Again, it helps to read the manufacturers instructions for the varnish you are using. There are many different products that are called varnishes. They are not all applied, thinned and/ or prepared for the same way.
Regards, John