If I will not be able to wear all of the clean clothes before the onset of the 9 days, it is acceptable to either put them on the floor for a few minutes or mix them with work clothing to “make them no longer freshly washed?” How would this apply to shoes that have been through the washing machine?
This idea is mentioned in the poskim. Regarding putting them on the floor, it means a floor that was not swept beforehand, so that the clothes will pick up some of the dust and dirt. I don’t know what you mean by mixing them with work clothing. The idea of putting them in the hamper so that they will no longer smell like clean clothes. The poskim say that it should be on the floor for about an hour. Regarding shoes, putting them on the floor won’t do the job, but putting them into the hamper should take the fresh smell out of them. Alternatively, if they are shoes that are befitting to wear on Shabbos, you can wear them on Shabbos, and then after that they can be worn during the week. Some of the poskim that suggest this idea say that they should be worn for a significant amount of time, otherwise it is considered preparing them from Shabbos for the weekdays.
The Three Weeks pg. 87 in the name of R’ Eliyashiv zt”l, Minchas Yitzchok 10-44, Teshuvos Vhanhagos 5-170, B’tzel Hachochma 4-138, Kol Hamisabel Oleha 14-6(3), ftnt. 40