The method I have found works best for me is to apply a liberal coat of epoxy and let it sit on the wood surface until it begins to set up. I wait for it to get to about the consistency of honey. I haven't timed it but I think it's about 30 minutes, maybe 40. What I do is apply the epoxy, then take the mixing cup with the excess epoxy in it with me upstairs while I wait, checking the epoxy in the cup with the mixing stick frequently to see if it's beginning to thicken. When it starts thickening I head back down to my shop. I use a single edge razor with the corners rounded over to "squeegee" off the excess epoxy from the wood surface. I wipe the epoxy off the blade with a paper towel after each swipe.

I find several benefits to doing it this way as opposed to using a squeegee to apply the epoxy and remove the excess immediately: 1) it allows the epoxy more time to soak into the pores, helping ensure they get completely filled, 2) removing the epoxy after it has thickened seems to avoid the epoxy getting "dragged" out of the pores, as happens to some degree when using a squeegee or credit card to remove the excess while the epoxy is still thin. So, only one coat is required to fill the pores, rather than 2 or 3 coats, and 3) the razor blade leaves a VERY thin coat on the surface so very little sanding is required before padding on the final, diluted coat.

I let the pore fill coat set overnight and apply the diluted coat first thing in the morning. First, I scrape the surface with a single edge razor (corners rounded over to avoid scratches) to remove any ridges in the cured epoxy. Then I sand very lightly (I think I used 400, but it probably doesn't matter much). I add roughly 2 parts alcohol to 1 part thoroughly mixed epoxy, mix well and pad on with a folded paper towel.

I would probably wait 3 - 4 days for that final thinned coat to dry before beginning your French polishing. You should probably try this thinned coat on scrap first to make sure it cures nice and hard with your epoxy / alcohol combination.

Using the above method I have not noticed any shrink-back of the epoxy in the pores.

Also, if you find your pore fill coat didn't completely fill all the pores, you could do a second coat the morning following the first application, then do the diluted coat that evening. I like to wait less than 24 hours between epoxy coats so they bond chemically as well as mechanically.