I rarely pull slides out for cleaning though sometimes it is best. Most times, I first use a can of penetrating lube and spray the crap out of the slides, using nozzle extension making sure to get everything I can.
Most of the times the drawers work well, or well enough. Sometimes I will hot pressure wash the slides with the drawers in place, then hit with lube.
Only as a last resort will I pull the drawers out. Lot of work and pain to reinstall drawers.