Alex Ferguson/wenger/clough etc all signed duds…NO ONE has a 100% record when it comes to transfers. Moyes however got lot more right than he did wrong.
If you look at his entire transfer history I'd say it is not quite as impressive.
From most expensive:
Fellaini, Yakubu, Johnson, Bilyaletdinov, Beattie, van der Meyde, Mirallas, Baines, Kroldrup, Heitinga, Jelavic, Lescott, Distin, Yobo, Jagielka, Pienaar, Wright, Neville, Davies, Oviedo, Howard, Stones, Arteta, Cahill, Valente, Baardsen, McFadden, Gosling, M. Gueye, Kilbane, Silva, Martyn, Bent, Jutkiewicz, Gibson, Ruddy, Vellios, Kennedy, Turner, Coleman.
Those were signings that he paid money for. Loads of duds in his frees and loan players. Half of his ten most expensive signings were duds.
I could list the freebies as well: Li Tie, Bosnar, Plessis, Stubbs, Wessels, Jacobsen, Saha, Peterlin, Mucha, Beckford, Hahnemann, Junior, Naismith, Nash, Neill, Hitzlsperger.
Loans: Donovan, Said, Ferrari, Fernandes, Castillo, Rodrigo, Weifeng Li, McBride, Jeffers, Westerveld, Jo, Senderos, Drenthe, Straqualursi.
Plus of course Pienaar, Arteta, Howard and Yobo were initially loans.
So he did find good players on loan.
(Based on Transfermarkt.)