No, there is no other way, apart from farming. You need to find contact which can help you in that. He/she needs to load the van and then you will rob. It's a fast achievement, if you can spend couple of consistent hours. Yeah so since there are hardly any cops, so you need to tell someone to be a temporary cop and then you can be thief. But you better start doing vehicle and house rob, and whenever your helper is online, you switch back to money rob mode. And when helper is offline, turn back to vehicle/house rob. In this way, you are not bored, and you finish your 3 thief jobs.
Location is the key factor, ROB only in North LV. Key locations : LV Bank, LV Cop Station, KACC Military Fuels, Spynbed, Sobell Rail Yards, Redsands etc. Then only you will get shorter unloads like Redsands, Admin Storehouse (LV), Verdant Meadows, or in the worst case Fort Carson.
But if you rob somewhere else like in South LV or central, then you will get long unloads like Red Country etc, so just stick to North LV. There are 3 base which are situated in North LV, just remember to spawn anyone of these which has good number of securicars. I'd say make one base as the main spawn point. Join a CB to stay in touch with helper.