Handling “hard dried stuff” in the black tank ?

Hard layer in bottom, for quite a while. Have been using the super friendly environmentally safe stuff, for quite a while. Tried letting it sit long time,did nothing.Tried soaps, bumpy roads, did nothing. So,when I went away (on the 7th), had found some old style now illegal? stuff, Thetford aqua-kem ultra concentrate.Added a bit of water and that, before I left.2.5 bags of ice.Well,having a toilet right on top of the tank,only so much ice would drop,must be a splash baffle.So when I would stop to pee,I would drop in more ice,till all was in. About 5.5 hr drive,one way, 2 hrs rough dirt and gravel,each way. Same road as last year,when I tried soap. Stayed a week, Got home to 30" of snow so camper/truck been sitting. Has warmed up, snow mostly gone, so 4 days ago dumped the tank. Got hose and wand ready. After dumping, looked in tank,(good flashlight!), all was very clean! Did not need wand, just hosed from back a bit, and very little of anything came out. This is what worked for me.