If your semen takes more time to liquify,it means it remains thick for more time and hence may cause problem in conception ,since you require thin semen to flow in at the time of sex.
Since GUAFENASIN found in cough
syrups help in thinning the semen,your doctor has prescribed you a cough syrup.
Other ways to increase the thinning of semen are...
Taking more of water and less of dehydrating drinks like alcohol,tea,coffee etc.
Take healthy foods like whole grains,green vegetables and fruits and avoiding junk foods.
Taking a multivitamin
Taking VIT E regularly.
I hope it helps.