Pricing of Jobs / other work

I’ve been on the tar for a couple of years now, with all the rates set out and I’ve never had to do any ‘other’ work, but recently I’ve been thinking about doing a few other bits when the plant is quiet. Since being an owner driver iv never had to go and look for work as the tar plant keeps me quite busy most days and I wouldn’t know how to price a job up in other parts of the trade ie limestone, gravel, top soil, plainings etc. Is there anyone willing to give me any advice on where to start? Iv joined return loads.com but 90% of work is for flat beds and curtain siders, so not much use to me with a rigid tipper. I’ve asked a few other owner drivers in the tar plant I run out of but nobody wants to give you advice as they think I’m going to rob there work lol. I’m just trying to get an idea of how to find work, I’ve not been lucky enough to come from a truck based family background to get any help, Iv just started from scratch and wondering, does most work just come from word of mouth or is there something I’m missing. Any advice or help would be much appreciated

Thanks

Mik