Whether or not we accept this relates to our understanding of what constitutes a vocation and how the virtue of being an artist fits into that.
In regard to painting sacred art, there are a number of elements needed: artistic skill; knowledge and understanding of the visual vocabulary and how it relates to the theological view it is portraying (in iconography it is Eschatological Man that is portrayed); and then the artist must have the virtue that allows him to follow God's grace to this end, should God choose to give it.
In this last respect, the principles of prayer (including that prayer directed towards a particular vocation) and fasting, are as much part of traditional Catholic, Western Rite spirituality as they are Eastern Rite. They apply to all artists, not just iconographers, who need inspiration and need to know how to follow it. There are three legitimate Catholic liturgical traditions, as specified by Pope Benedict in the Spirit of the Liturgy: the iconographic, the baroque and the gothic. And the need to for prayer and fasting applies to these other artists as much as it does icon painting. In fact, all Catholics should pray and fast and seek guidance in following their vocation, whatever it is. Artists are no different from accountants and janitors in this respect. Prayer and fasting is, and always has been, part of the spirituality of ordinary Catholics.
Another point worth making is that iconography is not an exclusively Eastern form. It is a traditional Western form as well. For example, Celtic, Ottonian, Carolingian and Romanesque figurative art forms are all consistent with the iconographic. So it is as much the art of the Western liturgy as it is of the Eastern. The West has also developed art that has a different theological focus but is nevertheless legitimately Catholic and liturgical, as Pope Benedict XVI has pointed out. Nor has the tradition of iconography in the East been an unbroken one. While the East had no Renaissance, its art did suffer from the effects of the Enlightenment. It only reestablished a truer iconographic form in the 20th century, with figures such as Photius Kontoglou. Much of what is transmitted as the rules of iconography, has been developed since this period. This started off as a rigid process in order to ensure its purity, but it has been interesting that even in the time I have been learning about iconography and icons (about 20 years, with the last 10 or so in greater earnest) as study and scientific investigation, such as through X-ray techniques, of traditional icons increase, many of these rules have been relaxed, to be replaced by a greater understanding of the principles that underlie them. These developments in understanding have been adopted by my Orthodox teacher.
Surprisingly many of these show that the methods of Western artists, such as those outlined in Cenino Cenini's textbook of the gothic middle ages, are more consistent with the original methods of iconography than those used in the East at the same time. Once one understands more deeply the boundaries that define the tradition within which one is working, it allows for greater freedom to move within them. This moves away from a restricting archeologism and gives us a living tradition that knows itself sufficiently to develop in response to its time and place without compromising the principles that define it.
A number of quality of Catholic icon painters are beginning to come through now. There are admittedly fewer than the Orthodox, because we are something like 75 years behind in reestablishing the principles of liturgical art, but they are there. I think of Sr Petra Clare in Scotland, for example: http://www.sanctiangeli.org/
This resource is provided in collaboration with The Foundation for Sacred Arts.