For recrystallizing P-anisidine, you could consider using solvents like ethanol, methanol, or a mixture of ethanol and water. For DNP, solvents like acetone, ethyl acetate, or a mixture of dichloromethane and methanol might work well. Keep in mind the solubility of the compounds and the compatibility with the specific schiff base you've synthesized. Always perform a small-scale trial to determine the best solvent for recrystallization.

I agree Lassaad Hedhill's opinions.

You might think about combining ethanol and water to recrystallize p-anisidine. For DNP, solvents for recrystallization, such as ethyl acetate, n-butyl alcohol, or a dichloromethane/methanol mixture, might be effective.

Birds of a feather flock together. In other word, like dissolve like.

Mixture of dichloromethane and methanol may be a prominent solvent. It may work effectively.

p-Anisidine turns black due to areal oxidation and even recrystallization using active charcoal too some times no better quality of desirable purity of p-anisidine is obtained. For purification it is best to distill p-anisidine under reduced pressure (avoiding use of water circulation in the condenser) . I have purified p-anisidine many times by distillation under reduced pressure to obtain -anisidine as perfectly white / colorless solid.

DNP (or DNPH) normally is a easily available commercial material. If required it can be purified by recrystallization with MeOH or EtOH using little co-solvents like dicholomethane or benzene (hazardous, to be used with care). But normally it is not necessary to purify DNP itself. For preparation of 2,4-dinitrophenyl hydrazone derivatives, DNP solution (Brady's reagent) is used. To prepare Brady's reagent dissolve commercial DNP (4 gm) in MeOH (85-100 ml) (taken in a dry 250-500 ml beaker) by slow and gradual addition of about 15-20 ml of conc. H2SO4 with stirring (external cooling may be necessary) till DNP dissolves completely and goes into solution (please stop addition of sulphuric acid as soon as DNP dissolves completely). On cooling to room temperature some crystal of DNP salt (light yellow needles) may appear.....filter it or dissolve it with little more MeOH to obtain clear Braddy's reagent. This is sufficienly pure for use.