SER trains as pitifully slow they are they are not exactly crawlers, the worst example of a crawler run by SER is East Coast:P
Crawler trains are a ER/ECR speciality... the HWH-MGS main line the best place to experience it freehand!
See, once upon a time not so far ago, when IR's daily operation defied common sense, there was a legendary train called HWH-DLI Janata Express! I have had the greatest fortune to make a HWH-MGS trip on this train and trust me, it was truly an outworldy experience:P
Similar...
more... was the Lal quila which was later restricted upto MGS & finally cancelled all together, the 'Rocket' KOAA-ANVT suffered a similar fate too and now runs as KOAA-PNBE express...
Now the best crawler experience that you can get is through Toofan, try it once, but don't blame afterwards :P