First of all, D-76/ID-11 1:1 would probably give you visibly finer grain than Xtol...but you'll still get rather fine grain with Xtol. Although I can't give you a development time I'd suggest using Xtol at 1:1 at least; full-strength Xtol gives the lowest EI and acutance.(posted 8642 days ago)Use standard stop, 30 seconds or so.
Fix in film-strength (1:3 or 1:4 depending on brand) rapid fixer three to six minutes depending on temperature with continuous agitation. Most fix problems with t-grain type films are caused by a combination of insufficient time and insufficient agitation.
After the fix, bathe the film in an HCA for a couple of minutes. You can use either the store-bought stuff or make your own by mixing 20g sodium sulfite and 5g sodium bisulfite in a liter of water. Although you don't _have_ to use an HCA, it'll clear the dyes and you won't have magenta negs which people keep howling and panicking about.
Wash 20-30 minutes.
As for a prewet, Ilford generally recommends against it because their films incorporate a wetting agent in the emulsion and since a prewet may remove this wetting agent unevenly, uneven development may result. So don't do it unless a problem appears that may be solved by using a brief prewet.
If you're using rotary processing, that problem may appear as airbells that aren't dislodged; in that case go ahead and use a prewet of about one minute. There's no need to prewet any longer than that.
BTW, before you get too deep into testing Delta 400, there's a new version coming onto the market that's expected to be rather different than the current/old version.