Feed little and often, as with most baits, to build your swim up.
It can take hours, so be prepared for a long wait; some places respond quite quickly and others will not so you may want to pre-bait (couple of handfuls) one swim and fish another, you then have the option of two methods.
Hemp will often be taken on the drop once the fish are 'Havin It', so there are two reasons to keep any shot around the base of your float:
1) Your hook bait will fall more slowly
2) The fish will try to take your shot
You will need to watch your float like a hawk for any signs of activity as this might tell you what's going on such as if they are up in the water.
Minnows will have hemp, so be ready.
Search your swim, often the bigger fish will hold back away from the main shoal / feeding area, so you could try to cast around the area where you are feeding. You could (contrary to above advice) put a slightly bigger float on if they are feeding well and put shot closer to your hook (e.b. 200 - 300mm) to get your bait through the small stuff of draw it back into your feeding area. If you use small shot (down the line as in above), bunch it together, it doesn;t always work, but it can put the fish off going for your shot.
Occasional bread punch hook bait may reward you with a bonus fish.
Food for thought I hope, well done for using hemp, it can be such a good bait on its day.