Regarding CitraSolv or any other “natural” solvent – Gamblin Colors recommended you test it out by letting it sit out, ie a few drops in a metal tin (non-absorbent) and if it evaporates away completely with no sticky residue – it should be okay. Turpenoid Natural left a sticky residue behind which can turn brown; just do the test first.
Pam notes: I use Citri-Solv ONLY to clean dried tins that held oil paint and to clean my tables but I do not use it in any mixture of paint that is applied to a panel or paper. I did the test as described above and it did indeed leave a sticky residue. I don't want sticky residues in my paintings! ;)