I can help!
With the advent of the Fleet Carrier update, the mining system was randomized. Lucrative mining opportunities are further out there than before.
My fleet carrier, MINER SUPPLY CO [X2L-13F], is currently parked 79ls from the richest Double Painite hotspot currently known, in the GCRV 1568 system.
At the midpoint between the hotspots, every second rock assays at between 20 and 60% Painite.
I stock limpets and all the mining accessories.
Unfortunately FDEV in their wisdom, capped the carrier's max buy price of any mineral to 10 times the galactic average price, so no carrier operator can offer competitive prices.... but you can sell you cargo at my carrier for 405k/ton, restock limpets and be back in the field mining in 10 minutes. You get a higher return per hour of grind.
The alternative is to use INARA or EDDB to find a high sell system and risk the long and pirate infested route to it. Don't forget your fuel scoop.
You can get about 790k/ton if you want to travel 200+ly to a high sell system.
For those who want to get max price in the bubble, you are welcome to fuel up here before heading out.
If I'm in game when you visit, hit me up and we could go prospecting as a wing... I've got a corvette that can break up a 'roid in a few seconds for you. I enjoy helping out other players.