Plywood is available in various grades (A, B, C), sanded and unsanded, veneer core or MDF core, and with surfaces of various kinds of woods. I'm not aware of any plywood that will emulate the friction coefficient of Delrin (polyoxymethylene).
With some hard, tightly grained, or oily woods (eg ironwood, ebony, teak) or Baltic Birch plywood, it might be possible to polish the wood to a point that its smoothness approaches that of polyoxymethylene. Note that those woods might cost more than polyoxymethylene does.
For other woods, it might be possible to use a filler and an epoxy finish to emulate some properties of Delrin, but if your project is about building your robot and not about accurately emulating properties of polyoxymethylene, I don't recommend the approach of experimenting with different finishes on plywood.
Instead, it may be best to purchase several polyethylene cutting boards and cut them up for use as polyoxymethylene testing standins. Large cutting boards often are available cheap on Ebay, and small cutting boards can be found at thrift stores.
Note that polyoxymethylene is significantly stronger, harder, and more wear-resistant than the polyethylene in cutting boards, but polyethylene's properties are so much closer to polyoxymethylene's than plywood's are, that the prototyping fit should be much closer. For a still-closer fit, you can buy “drops” (small cutoffs) of UHMWPE (ultra high molecular weight polyethylene) that in some applications will work as a Delrin replacement.