• I am not familiar with the use of glycerol in this context but with ref to drying of DNA and especially RNA the main thing to avoid is vacuum drying as this desiccates the pellet and makes dissolving more difficult; especially for RNA
• I would say and I personally dry DNA at room temp for ~15 minutes and RNA on ice for ~15 min followed by 10 min at room temp
• In both cases with pure sample an opaque pellet turns transparent (unless salt contaminated) and that tells you the pellet is 'touch' dry and ready to dissolve in water or TE 

I hope I havn't misconstrued your question !!

I haver just come across this answer in the context of glycerol and RNA/DNA precipitation

https://www.researchgate.net/post/what_is_the_purpose_of_glycerol_and_difference_between_isoprpanol_and_ethanol_during_rna_dna_isolation

it may cause not proper drying. As glycerol dissolves in water.