I've not used the toe grips, but have heard of others using them with success. One thing to remember is that with or without the toe grips, you still have to keep the nails trimmed, the shorter the better. Many breeds, mine included, grow quite a bit of hair between the pads of their feet. Keeping it trimmed flush with the footpads will also help with slipping on tile and vinyl.
An overweight dog is going to have more problems as it ages with staying on its feet.
Finally, the slipping in a senior dog may be a symptom of IVDD, DM, or a variety of other unpleasant realities of aging pets. Been there, it's horrible.