You do not want the Gramercy brush for Epifanes. Epifanes (at least unthinned or even lightly thinned) is a very thick product and the Gramercy brush though beautiful, is very very soft. You would have to thin the Epifanes consideraby to use the Grammercy. The bruhes that Epifanes Distributors sell are Italian Omega brushes and are very full and pretty stiff and Epifanes carries them for a reason. They are good at pushing a stiff product.
In general all you need is a good quality professional brush available at any paint store or Depot. People have their individual favorites. Unfortunately the brush will not make the job. An expensive brush will not automatically give you a great job. I've tried and owned virtually every brush out there. Also consider that you will have to clean it and especially an expensive one (and they are pretty well all not cheap) and clean it meticulously. You don't want a real cheap brush. But then again you can get a good quality brush pretty reasonably. Corana Urethaner is a good inexpensive brush and there are others. And the Urethaner would push the Epifanes. Getting the hang of Epifanes and thinning it to handle for different conditions and different abilities, now that is a whole other story. There are far easier varnishes to use than Epifanes.