You didn't say what type of coaming and lip you're making - stacked plywood or a Nick style with upright pieces etc. Don't glass the lip edge because you're only asking for disaster and a lot of swearing. Fo our purposes, glass cloth is a binding substrate to hold things together like a girdle. Epoxy by itself will finally cure rock hard and is actually more abrasion resistant than glass cloth. You can see this if you ever sand a boat for a repair. In all cases I glass my coaming but just coat my lip with several coats of epoxy. If you do a stacked coaming (Chesapeake style) you could glass the coaming if you want but it's not needed. Trying to glass a lip or lip edge is foolish and not needed - it's plenty strong enough and a nightmare challenge with no real benefits.