Combining lawn treatments for moss and crab grass

[MisterBoy]

As well as a little moss and normal weeds, the main issue I have in my small lawn is an invasion of crab grass.
Looking online, you can get special products to prevent it germinating, and specific herbicides to kill it, both of which shouldn't kill the lawn itself.

I assume it's too late to prevent germination now the grass is growing this year?

I haven't applied any treatment to the lawn since autumn so how can I best treat it now? I have a generic weed/feed product (Westland) which contains ferrous sulphate for moss, 12-2-4 fertiliser and unspecified herbicides, but I don't think this targets crab grass.
I need to make sure I don't overdose by combining products so can I add a specialist crab grass herbicide to what I've already got and do one combined application? Or do I need to buy individual products and mix my own?

 

[MisterBoy]

A bit more research seems to indicate you cannot buy crabgrass products in the UK... is that the case? Is it possible a professional might have access to them if so?

 

[johnny2007]

I used weedol with success.
I bought a concentrate bottle and it goes a long way.

 

[MisterBoy]

I used weedol with success.
I bought a concentrate bottle and it goes a long way.

Surely that kills everything though?

 

[johnny2007]

Surely that kills everything though?

No, it's a lawn weedkiller.
Kills weed, not the lawn.
I now use it to spot weed.

 

[MisterBoy]

No, it's a lawn weedkiller.
Kills weed, not the lawn.
I now use it to spot weed.

Far as I can see, most lawn weed-killers don't target weed grasses only non-grass weeds? I've got some of that (or equivalent) but since my fertiliser includes weedkiller I'm not sure double-dosing would be a good idea.