The textile glue is actually latex and remains very 'rubbery'. The felt enables it to remain on the feet, otherwise it'd peel right off again. The felt can be glued to the hardened feet with the textile glue. Alternatively a spot of superglue (can also be removed again, dissolves with hot water).
For example the feet on this Corona Speedline typewriter had no grip on the table. Still pliant and 'rubber', but no grip.
A light sanding to roughen-up the circular 'base' of the rubber feet and a set of 1mm thick wool-felt pads ready to be glued on. A dab of the latex textile-glue and ready to be pressed on.
After setting of the pads, another small drop of latex is applied on the centre of the pad and given time to set well - that will then provide ample grip and not come unstuck from the thin felt layer. Depending on how much the visual appearance matters (the base of feet are not generally visible...), extra care can be taken on where to avoid getting the latex or to get an even coverage. As it is, went for functionality mainly.
