Hello Hopeful, your post reminds me very much of the problem I have with therapy.
For a long time I blamed myself for being too intellectualized and analytical and tried very hard to stop the endless thinking about and focus on feelings instead, until I realized that none of my therapists were the slightest bit interested in helping me get in touch with how I felt anyway. I suspect because their approach was based much more on helping people with out of control emotions rather than people like me who have huge problems feeling their feelings in the first place.
So despite my best efforts at trying to feel instead of rationalize, I found that the Ts themselves were more or less either actively discouraging the expression of feelings and instead encouraging talking ABOUT them (which just exacerbated my propensity to rationalize and analyze and explain everything cognitively) or they expected me to be able to 'emote' all by myself in a vacuum.
I'm assuming that your T is not as lousy and inexperienced as the ones I've seen were, and therefore wonder if it might not be useful for you to talk to her more openly about helping you get in touch with how you feel? I found that it would have been so much more useful had my Ts done the cliche of asking 'how are you feeling now' - some way of grounding me in the moment and experiencing what I was feeling instead of using my mind to keep myself three steps removed from my own experience. It sounds like maybe you are similar, and talking to your T about exactly what you want from her in terms of overcoming your intellectualizing might be a useful thing to do?
Also, you talking about slowing down once you do get a flash of a feeling, YES. Only, easy said not so easy done, if your set up is such that you instinctively and automatically jump in with the thinking and rationalizing the moment you feel something - that's where you need T to be able to intervene and keep you focused on the feeling. Like you I tell myself, slow down, take my time, sit with the feeling but for the life of me I can't stop the observing thinker from getting in on the act (what does that mean, what does that tell me - bad - about myself, why am I feeling this...) and by that time the feeling has long gone. Having someone else take the place of the observing thinker is a way of breaking that instinctive (and defensive!) pattern.
Oh dear I didn't set out to pontificate like this, I hope what I've written is in some way useful, it's only my own experience of what I think is a similar set up to yours
LL