Departing IFR at SMO w/ Tower Closed

Ok, here is a hypothetical question about departing from Santa Monica
and about IFR departures at uncontrolled fields in general. Suppose it
is after 9pm (the tower is closed) but before 11pm (departures still
permitted). Assuming that the field is IFR, what would be the proper
way to obtain clearance and depart? Is there an RCO on or near the
field to allow communciations with SoCal departure, or does one need to
phone in to get the clearance?

Also, "Takeoff Minimums" are listed as follows:

SANTA MONICA, CA
SANTA MONICA MUNI
TAKE-OFF MINIMUMS: Rwy 3, 700-2 or
climb of 290' per NM to 1000.
DEPARTURE PROCEDU Rwy 3, climb
climbing right turn direct SMO VOR/DME.
SMO R-261 to SADDE Int. Rwy 21, climbing
to intercept SMO R-250 and FIM R-148
All aircraft continue climb on course.

My question is twofold:
1. What is the proper procedure for SMO?

2. What would the proper procedure be for an uncontrolled/closed tower
field after hours with such a departure procedure listed, assuming a
clearance with void time, etc? Would I expect ATC to specify this
procedure in my clearance? Would executing this DP be at my
discretion? Obviously for obstacle clearance it might be advisable.
Would I need to inform ATC? What if it conflicted with the clearance I
was issued? How would this work?

Thanks,
Dan