This has been discussed quite a few times already, so check the archives for more.
MGIV fibre is not a paper that reacts to Selenium readily, though it can be persuaded.
This is what I do. I dev in Ilford multigrade, ilfostop and fix it for one minute in Ilford rapid fix. Then it's a 20 minute wash in running water before toning.
I use KRS 1+4, at 22-25 degrees C, for 5 - 10 minutes. This increases D-max and gives the paper a blue/purple/charcoally look that suits my street/reportage style. I then wash for one hour again in running water.
I find that the RC paper while still not that keen to react with KRS does so much more readily than the fibre version.