N'Guessan, who fell out with Lions fans and former boss Kenny Jackett last season, had his contract terminated on transfer deadline day so he could join Swindon.
And Lomas has since used the funds freed up to extend the loan of QPR midfielder Derry and bring in Leicester striker Waghorn until January.
"We were able to get Dany out and use the money for both Derry and Waghorn so we are delighted, for me it's the deal of the century," Lomas told Press Association Sport.
Waghorn is likely to make his debut against Derby on Saturday and Lomas revealed he had taken a pay cut to help push the move through having fallen out of favour at Leicester.
"Leicester have contributed and so has Martyn, which proves he just wants to play football," added Lomas.
"He's 24, he knows the league but he hasn't had much of a chance due to the strikers Leicester have had over the last couple of years. He's got quality and he's hungry."