Originally Posted by The Cavalier

LIRR will not help him at all from LGA only from JFK to EWR via Penn Station.

Here is the answer he is looking for in absence of the FA's crew runner.

From LGA: Q70 bus to Jackson Heights station (it's the only stop and takes approx 15 mins). From Jackson Heights take the E train to 34th Street (Penn Station) which takes about 30 mins. Once in Penn Station take the NJ Transit to EWR. 1.5 hrs is sufficient to make the trip and it is very easy.

Time wise the travel time is the same whether you use the crew runner or public transportation.