In the case of Gomess, it is said that the Godzilla costume used in the 1964 Toho movie “Mothra vs. Godzilla” was assigned the role of Gomess, the monster which highlighted the commemorative first episode of Ultra Q (in the broadcast order).
As they had to return the Godzilla costume borrowed from Toho naturally after the shooting was finished, a means seems to have been devised to make it look like another kaiju and to give it back to Toho without inflicting any damage on the costume.
It came in the form of temporarily making the costume wear a vest-like surface texture including the parts with scales put onto the Godzilla costume to avoid fiddling with the suit itself and keeping it free from damage which can possibly be caused by cutting and such.
It is also explained he wore a wig with the horn attached to it and his fangs were fixed with wire without the use of adhesive, and it seems that he had his whiskers grow to hide the wire.
I think it is a great job to make Godzilla excellently look like another monster by simply equipping the costume with such appliances.
At the same time, that shows there was no idea yet of featuring completely original kaijus for the new TV show, Ultra Q, and Godzilla should have been the synonym for the kaiju in those days.
Gomess was designed by Yasuyuki Inoue who was with the Toho Special Arts Division back then involved in the Toho kaiju movies including Godzilla while the Ultra Q kaiju was also played by Haruo Nakajima known as the original Godzilla actor.
The appliances are also said to have been made by the Toho Special Arts Division, and Gomess’s horn seems to exist even now.