Is your mesh doubled? Meaning is there an outside and an inside or just an outside mesh. If it is doubled and has an inside mesh using a mask and turning on BackFace Mask in the AutoMask Brush Menu while holding the Command or CTRL key draw a mask on the inside or outside depending which is easier then inflate. If you masked the outside and want that inflated just select the inverse button in the mask section of the tool menu.
If it is not doubled then it needs to be. Use the extract and you will get a back and a front as well as an edge between both, remember to turn off doubled, TCorner, TBorder and make the initial extract fairly thin. Hit accept. Now select the inside or outside poly group mask it and then inverse the mask and now inflate.
tip you can also bennifit from making poly groups to hide and select certain parts for other things like texturing and painting. In Max you can make your own poly groups by using then subdevide group ID’s I think they are called I haven’t been on Max for sometime but it has a whole bunch of little boxes with numbers on it in the tool. In ZB you can make poly groups by using the Command or CTRL key and W and it will make a new poly group out of any mask.
hope this helps.